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Aug 172012

Dr. Lloyd Glenn Ingles © California Academy of Sciences

What are deer doing in my yard?

Idaho’s mule deer and white-tailed deer are “edge” species, preferring to browse in open areas near forests or dense shrubs. Our urban landscapes, with their innumerable edges, are consequently very attractive to deer. On average, deer eat about 7 pounds of food—approximately 3 percent of their body weight—each day. They’re most active in the early morning and evening. Deer like to nibble, tasting first one plant, then another, and will return to your yard repeatedly if they’ve learned they’ll find good things to eat there. While they like some plants—and some stages of plant life—better than others, they’re far from fussy. Deer also drink 2 to 4 quarts of water a day, sometimes from birdbaths or water features. Females typically, they have one or two fawns each spring, although triplets are not unusual for white-tails.

Benefits and conflicts

Who doesn’t enjoy watching these graceful animals, especially with their adorable fawns at their sides? However, deer can cause extensive damage to urban landscapes, orchards, and vegetable gardens by feeding and trampling on plants and by rubbing antlers against young trees and shrubs. Young garden and landscape plants can be severely damaged or killed by these visitors’ spring and summer browsing; indeed, deer have a special yen for tender new shoots and buds. Deer will include fruit in their diet during the summer, acorns during the fall, and lichen, dead leaves, twigs, bark, and evergreen boughs in the winter.

Strategies for coexistence and control

Habitat modification: Although deer become decreasingly selective as they become increasingly hungry, there are some plants they are less likely to eat. Among the plants that deer avoid are those with a strong scent, and those with thick, leathery or fuzzy leaves, or bristly or spiny textures. Many deer-resistant plants are poisonous throughout the year or at some stages of growth. See Deer-Resistant Plants from Colorado State University for more information, or deer-resistant plants from Oregon State University.

Fencing: Typically, it takes an 8-foot-tall fence—plastic mesh, wood, chain link, or wire—to keep deer from jumping into your yard. However, a 5-foot height solid fence may work because deer are reluctant to jump into an area they can’t see. Keep them from crawling under the fence by securing it close to the ground. Electric fencing—one to five wires temptingly baited with a 1:1 mixture of foil-wrapped peanut butter and peanut or vegetable oil—can effectively exclude deer from small areas. Successfully lured into being shocked, they learn to stay out. Protect individual trees or shrubs by encircling the plants with staked wire or plastic mesh. Some commercially available trunk wraps are designed to protect bark from antler-rubbing.

Frightening devices and repellents: An active dog running loose in a fenced yard can effectively deter deer. Odor- or taste-based repellents can help if they’re applied repeatedly, especially after rain or irrigation, and if the same repellents aren’t used for too long. Once deer accommodate to a particular repellent, it loses its ability to deter them. Flashing lights, for example, work briefly but deer soon learn to ignore them. If you’re spraying a repellent on a food product, be sure to check the product label to verify that that is an approved use.

Trapping: Constraints of labor and expense usually make live-trapping and removing deer unfeasible.

For more information
 August 17, 2012
Aug 172012
MarmotWhat is a marmot doing in my yard?

In Idaho, we use the name rockchuck for the yellow-bellied marmot (Marmota flaviventris).  In some places they are also called “whistle pigs.”  Marmots are rodents and are the largest member of the squirrel family.   They look like an overgrown ground squirrel with a yellow-tan belly.  Males can weigh as much as 11 pounds.

Marmots live among rocks where they can find and build burrows.  Luckily, they do not indiscriminately dig burrows in open ground like their eastern “woodchuck” cousins. They are common in Idaho’s warm valleys and are often seen in the foothills, even near cities, and also around the edges of lava formations. It is a common site in southern Idaho to see yellow-bellied marmots in springtime sunning themselves on rocks along roadsides.  In the summertime, marmots mostly emerge from their dens and feed at night. For that reason, it is sometimes hard to identify the culprit when damage is discovered in the garden.

Marmots tend to live in social colonies, are prolific breeders,  and can become serious garden pests if present in large numbers.  Marmots will eat any tender, green plants but especially love succulent vegetables.  They are voracious and a few marmots can strip a vegetable garden in a few nights. Marmot damage is unique in that they eat plants to the ground, giving them a “mowed” look. Other pests tend to be selective in what they eat.

Benefits and conflicts

Marmots provide little direct benefit to the homeowner. They can be interesting to observe during the times of the year they are outside their burrows. Conflict with marmots come directly as a result of their tendency to raid the garden and eat anything that looks like a plant, including the lawn.

Strategies for coexistence and control

In agricultural areas, when marmot damage becomes severe, action is taken to eliminate the problem through shooting, gassing, or poisoning. For the homeowner, these options may not be appropriate for a number of reasons. Also, many gardeners are willing to share their produce, as long as the marmots do not take the lion’s share. Following are ideas for dealing with marmots if they become a problem.

Remove them through trapping: Live traps baited with succulent leaves or sprigs of clover can be used to capture marmots, which then can be moved to a more suitable habitat. To keep the pests from returning, relocate them to a place at least five miles away.  

Plant a “marmot garden:” If the marmots are not too numerous, you can keep them from damaging precious plants by planting an attractive feeding spot close to the den.  Given their preference, marmots will eat succulent clover over most other types of plants, so a plot of red or white pasture clover would be a good choice for your “marmot garden.”

Build a fence: Placing a marmot fence around choice vegetation can be a good alternative, but the job must be done right.  Marmots excel at both digging and climbing.  The fence must made of mesh wire, and be at least 4 feet tall and preferably bowed outward at the top with the bottom buried 12 to 18 inches into the ground. Or form an L-shaped fence with the lower edge leading outward and buried about 2 inches making it harder for the marmot to dig underneath. In reality, fences are of questionable value in keeping marmots at bay.  One exception to this is the use of electrified fencing with multiple wires spaced from just above ground level to about 2 feet up.

For more information
 August 17, 2012
Aug 172012

© 2005 Tom Greer

What is a rabbit doing in my yard?

Because Idaho’s mountain cottontails and white- and black-tailed jackrabbits can breed repeatedly from late winter through summer and can eat everything from tender vegetable shoots to tree bark, what they’re doing in your yard is probably eating, and reproducing. Cottontails can produce a new litter (typically, three to five young) as swiftly as monthly reproducing generally February through August. Jackrabbits take a little longer, 43 days gestation period, but may have up to 8 young per litter. Woody and dense vegetation appeals to cottontails, while jackrabbits favor open rangelands and cultivated fields. Although cottontails often seek shelter-hunkering down under brush piles or dense shrubs, hiding in sheds or hightailing it down the proverbial rabbit hole-jackrabbits typically protect themselves by fleeing (at speeds up to 40 miles per hour).

Benefits and conflicts

Rabbits can be fun to watch, if you’re not watching them eat something you’d rather they left alone. During the growing season, they’re particularly partial to tulips, carrots, peas, beans, lettuce, beets, and grass, although there’s not much in the garden or landscape they won’t eat if they’re sufficiently hungry. In fall and winter, they turn to young trees and woody shrubs, cleanly clipping off small stems, slicing off buds, or gnawing on the bark of young trees or shrubs. They can completely girdle and kill vulnerable woody plants.

Strategies for coexistence and control

Habitat modification: Remove piles of brush and stone and patches of tall weeds, particularly around vulnerable, newly planted trees or shrubs. Ironically, this sort of garden cleanliness discourages cottontails but pleases jackrabbits.

Fencing: Fortunately, rabbits are relatively simple to exclude from vegetable, herb, or flower patches with inexpensive fences or domes made of 1-inch or smaller-mesh chicken-wire. In the summer, a 2-foot-tall fence will deter cottontails and a 3-foot-tall fence will ward off jackrabbits. In the winter, you’ll want to build the fence higher to reflect your area’s anticipated snow depth. Either stake the bottom end of the fence tightly to the ground or splay it outward, burying the bent edge about 4 inches underground to thwart digging. Commercial cylinders or home-made cylinders of 1/4-inch hardwire cloth will protect young trees, as long as the cylinders are tall enough to keep rabbits’ incisors from reaching above them and far enough from the trunk to keep rabbits from chewing through them.

Frightening devices and repellents: A fleet-footed dog is best; many other repellents have been tried, with far more variable results. Read the label carefully; most repellents aren’t intended for use on human food and many must be reapplied after rainfall or irrigation.

Trapping: If you know of a gardener who wants the company, cottontails are easy to lure into traps and relocate. Be aware that the ecological niche the dearly departed rabbits will leave in your yard will most likely be filled by neighboring rabbits.

For more information
 August 17, 2012
Aug 172012

Dr. Lloyd Glenn Ingles © California Academy of Sciences

What is a raccoon doing in my yard?

The omnivorous, nocturnal, and nimble raccoon is either prowling for its preferred or staple foods or on the hunt for a den site. In addition to pet food and garbage, raccoons will eat plants (fruits, nuts, and vegetables) and animals (grubs, crickets, grasshoppers, frogs, worms, fish, turtles, squirrels, rabbits, rats, mice, bird eggs and nestlings, among others). Raccoons particularly fond of sweet corn and watermelons. In nature, raccoons will den in tree cavities, brush piles, or ground burrows. In our yards, these resourceful and often destructive critters will seek shelter in or under any structure they can enter. That includes attics, chimneys, crawl spaces, and wood stacks as well as the areas beneath porches, decks, and sheds.

Raccoons typically bear litters of roughly three to six young in April or May. These young will stay with their mothers for about a year. In urban and suburban areas, densities of well-adapted raccoons can reach 100 per square mile.

Benefits and conflicts

Raccoons will provide a little help with insect and rodent control, but they can quickly become pests themselves. Besides knocking over garbage cans, raiding vegetable gardens, stealing tree fruit, and rolling up freshly laid sod in search of grubs, they can establish dens in chimneys and rip off shingles or fascia boards to enter attics. They may also carry fleas, ticks, roundworms, rabies, and canine and feline parvovirus, among other potential health threats to humans and pets.

Strategies for coexistence and control

Habitat modification: If possible, remove woodpiles and trim overgrown shrubbery to reduce cover. Also, be sure to secure your garbage cans and lids and to bring pet food and water in overnight.

Exclusion: Before attempting exclusion procedures, be sure there are no young raccoons in the area from which you are attempting to keep the animals out of. Raccoons can readily scale fences and even open simple gates. A good way to keep them from clambering over or digging under your fence is to install a single electrified wire 8 inches from the fence and 8 inches above the ground. If you don’t have a fence, two parallel wires-mounted about 6 and 12 inches above the ground on insulated stakes-should also work.

A commercial sheet-metal chimney cap or heavy metal screen (installed only if you’re certain no young will be trapped inside) offers good protection against raccoons in your attic. Trimming tree branches back 3-5 feet from the roof also helps as long as you don’t have other landscape structures they can clamber up. To exclude raccoons from open spaces beneath structures, such as a patio, install 1/4 or 1/3-inch galvanized hardware mesh, burying the bottom edge at least 6 inches deep extending the buried portion outward about 12 inches.

Frightening devices and repellents: No chemical repellents have been proven effective against raccoons and no frightening devices will work for very long.

Trapping: Raccoons are relatively easily trapped but there may be restrictions about relocating. A trapped raccoon can also be very vicious, so it is advisable to contact a professional wildlife control operator for assistance.

For more information
 August 17, 2012
Aug 172012

© 2005 Kim Cabrera

What is a skunk doing in my yard?

Slow-moving, mild-mannered, and severely near-sighted, skunks are nocturnal and nomadic. When they visit your yard, they’re either looking for food or shelter or simply passing through. Mice, grasshoppers, beetles, crickets and other insects are all important components of the skunk diet. Skunks will also eat eggs, berries, carrion, snakes, frogs, small birds, rats, rabbits, and other small mammals and, of course, garbage and pet food.

To a skunk, the dark, quiet, and often protected areas under decks, porches, and sheds all look like good places to bunk for the near term. Abandoned woodchuck or fox burrows, rocky crevasses, culverts, hollow logs, and lumber piles make suitable dens as well.

Skunks typically bear one litter a year of two to 10 young. The young are born in May or June and are on their own by fall. The normal home range of a skunk is less than 2 square miles, although breeding males may travel up to 5 miles each night.

Benefits and conflicts

Skunks destroy large numbers of garden pests such as grasshopper and beetles. But they can burrow under porches, decks, and foundations and slip inside buildings through openings as small as 3-4 inches. Loose in the vegetable garden, they’ll waddle over to the sweet corn and eat the lowermost ears. Searching for grubs near the surface of wet lawns, they’ll dig 3- to 4-inch-wide cone-shaped holes or upturn small patches of turf. Most annoying of all, when threatened they’ll spray to distances of 15 feet or beyond. To their credit, they give fair warning by arching their backs, raising their tails, stamping their feet, and shuffling backwards. Uncommonly, skunks also carry rabies.

Strategies for coexistence and control

Habitat modification: You can minimize skunk-related problems by:

  • Keeping cellar, basement, and crawl space doors closed
  • Sealing and covering all openings, including window wells
  • Removing debris, brush piles, and lumber stacks
  • Keeping pet food inside
  • Covering garbage cans
  • Reducing grub and rodent populations
  • Preventing accumulation of ripe fruit on or below fruit trees
  • Taking precautions before letting dogs out at night

Fencing: Fortunately, skunks aren’t skilled at climbing and a fence will normally deter them. They are, however, exceedingly skilled at digging so you’ll need a 2-inch wire mesh fence that’s not only 3 feet high but that extends 6-12 inches below ground and another 6-12 inches below ground bent outward at a right angle.

Frightening devices and repellents: No repellents or toxicants are registered for skunks, although ammonia-soaked rags, loud radios, and bright lights in denning sites may encourage them to seek shelter elsewhere.

Trapping: Call a professional wildlife control operator if you feel a skunk must be removed. Be aware that another skunk is likely to take its place, filling the vacancy that removing the first skunk has left in the environment.

Fore more information
 August 17, 2012
Aug 172012
voleWhat is a vole doing in my yard?

These small, short-tailed, brown or gray rodents are active year-round, but you’re likely to see them only infrequently. They spend most of their time in burrows below ground. Especially during the peaks of their three- to five-year population cycles, voles are drawn to gardens and landscapes with deep mulch and litter and with dense, tall grasses and weeds. They tend to spend their entire, though brief, lives in an area smaller than a quarter acre. They can have one to five litters a year with about three to six young per litter.

Unlike pocket gophers, whose burrows are distinguishable by significant above-ground damage, voles leave few visible signs. They reveal their presence by the narrow, aboveground, grassy runways they use between their small burrow openings. Look closely and you’re likely to see grass clippings and small green droppings in the runways.

Benefits and conflicts

Voles can eat snails and insects, but that may not be enough to endear them to gardeners. In addition to temporarily damaging the turf in their runways by clipping it very close to the roots, voles feed on many different kinds of grasses, herbaceous plants, bulbs, and tubers. In the vegetable patch, they favor artichokes, beets, Brussels sprouts, cabbage, carrots, cauliflower, celery, lettuce, turnips, sweet potatoes, spinach, and tomatoes. In fall or late winter, they turn to the bark and roots of trees and shrubs, which they can damage significantly.

Strategies for coexistence and control

Habitat modification: Keep grasses mowed and remove weedy patches at your garden’s edge. Clear a 3- to 4-foot circle around the base of young trees or vines; voles don’t like to feed where they can be seen. Minimize spillage from bird feeders.

Fencing: Fortunately, voles don’t climb well. They can be thwarted by a fence made of 1/4-inch or smaller mesh that’s about 12-18 inches aboveground and 6-10 inches below ground. Similarly, cylinders made of 1/4-inch or smaller hardware cloth, sheet metal, or heavy plastic, pushed into the ground as deeply as possible without damaging plant roots, will protect young trees, vines, and ornamentals. Check these cylinders frequently to make sure the voles haven’t dug under them.

Frightening devices and repellents: Frightening devices are ineffective against voles and repellents offer only short-term effectiveness. Available poisons can be toxic to humans and pets as well as to nontarget wildlife.

Trapping: You can trap small populations of voles with mouse traps baited with a peanut butter-oatmeal mix. Set the traps at right angles to the runways, with the trigger ends in the runways. To reduce access by nontarget birds and other animals, cover the traps with a box through which you’ve cut a 1-inch hole or enclose the traps in PVC pipe. Check the traps daily. Because voles can carry infectious disease organisms or parasites, be sure to handle their remains with rubber gloves or similar protection.

For more information
 August 17, 2012
Aug 172012
water can

Water is key to container plant health

Principles for maintaining healthy plants in containers are no different than for plants in a garden. However, in practice, container plants require greater attention to detail. Limited soil volume and potential stress create requirements for frequent irrigation and fertilizer and constant monitoring for pests.


There is no easy way to schedule watering of container plants. During hot weather, irrigation may be needed every day. However, it should be recognized that overwatering of container plants is a more common cause of death than is underwatering. With that said, a rule of thumb is to let the top 1-2 inches of soil completely dry between irrigations. When applying water, add a sufficient quantity to allow some water to drain out the bottom of the pot.


A high level of fertility must be constantly maintained in containers to keep plants healthy and attractive. The two best methods for applying fertilizer are to 1) mix a slow-release granular fertilizer into the top few inches of soil in the spring and again in mid-summer, or 2) use a solution of a complete fertilizer once a week when irrigating the containers.

Pest Control

Many insect pests infest container plants to a greater degree than garden-grown plants, especially spider mites. Diseases also can become problematic, especially if plants are stressed. Plants should be monitored frequently to identify pest problems before damage becomes severe. Pest control methods for container plants are identical to those described in the other places in this web site (annuals, perennials, bulbs, Insect and Disease Pests).

Excellent information on container gardening is provided Chapter 19 of the Idaho Master Gardener Handbook.

Kansas State University provides detailed container garden instruction.

 August 17, 2012
Aug 172012

Once established, ornamental grasses tend to be relatively carefree. In general, they require little in the way of fertilizer and water inputs. However, as is true of all plants, some tender loving care is needed to keep them healthy and attractive.


If not done before planting, it is beneficial to mulch around ornamental grasses. This will keep the soil cool, retain moisture, and help with weed control.

hose running

Ornamental grasses need minimal water


Ornamental grasses, in general, should be irrigated less often and to a greater depth than other parts of the landscape. Some fescues and other drought tolerant grasses may need much less water overall. During July and August, a weekly irrigation with about 2 in. of water should be adequate in most soils. In sandy soils, less water should be applied on a more frequent basis. The amount of water applied should be cut back during the cooler spring months, the late fall, and during those infrequent periods of rain.


Most ornamental grasses need very little in the way of fertilizer. They may benefit from a spring application of a fertilizer high in nitrogen at the equivalent of 1-3 lbs nitrogen per 1,000 sq. ft. On the other hand, some years, no fertilizer of any kind may be needed. Determination of requirement is based on growth response. If the previous year, plants were slow growing, small, with yellow color, add some fertilizer.


Grasses can be cut back in fall or winter


The only consistent need for ornamental grasses is removal of dead leaves and flower spikes at the end of the season. For many species, those that break, shatter, or fall over in the winter, this should be done in late fall. For grasses that remain attractive through the winter, this can be done in early spring. Cut grasses back to a height of 4-5 inches before new growth appears.

Weed Control

There are no options to completely replace hand weeding in ornamental grasses. Mulching with organic matter or weed barriers will help by blocking germination and growth of weed seed. Perennial weeds that creep into beds create the most difficult problems. If hand cultivation provides inadequate control, it may be necessary to hand apply a herbicide, such as a glyphosate product, by hand with a sponge or other wicking material.

Icy grass

Grasses may benefit from winter protection

Winter Protection

Most adapted ornamental grasses can withstand winters without winter protection. However, a layer of mulch over the crown may allow the plants to be more vigorous in the spring. Proper winter mulching consists of application of 3-4 inches of compost, leaves, wood chips, or other organic matter. The mulch should be removed from around the crowns in early spring to help prevent premature growth of shoots that may be damaged by frost.

For more information on the general care of ornamental grasses, see the following two web sites:

Disease and Insect Control

Ornamental grasses have very few consistent pest problems. However, there are a few organisms that can infest grasses and make them less attractive. Some of these are listed below. For detailed information on control of these insects and diseases, as well as information on other pests, see the Insect and Disease Pests section of this site.

Insect Problems

Mealybugs: Are sucking insects, one species of which can become a problem on the Miscanthus grasses. Mealybugs are easily recognized by the presence of a cotton-like white substance they deposit for protection. In cases of serious infestation, the plants will be stunted and go dormant earlier than healthy plants.

Control of mealybugs can be had by spraying the plants with a direct stream of water, using and insecticidal soap, or using a registered insecticide.


Snails often live in the crowns of grasses

Slugs and Snails: Prefer damp soil and humid conditions. Slugs and snails often hide during the day and feed at night. Symptoms include chewed leafs and glistening slime trails on plant surfaces. Although slugs and snails will not do significant damage to most ornamental grasses, the thick foliage may provide a haven from which they will emerge and damage surrounding plants.

Control snails and slugs with baits.

Disease Problems

Leaf Rusts: Are caused by several related fungal pathogens that penetrate and kill leaf tissue. Symptoms are usually typified by a yellow, orange, or brownish discoloration of the upper leaf surface on older leaves. The leaves eventually decline and die. These diseases are usually worse following a wet spring.

Removal of all dead plant material at the end of the growing season helps prevent many leaf spot diseases in subsequent years. In-season control usually requires use of a registered fungicide. Maintaining overall plant health is important in controlling fungal leaf diseases. Ensuring proper aeration among plants will reduce humidity and slow the progress of rusts.

 August 17, 2012
Aug 172012

Bulbs do not require and excessive amount of care, but timing and quantity of inputs are unique relative to other perennials. Here is a guide to care for established bulb gardens.


If not done before planting, it is beneficial to mulch the bulb flower bed before heat of summer sets in. This will keep the soil cool, retain moisture, and help with weed control.


Bulbs require deep watering


Bulbs have a range of water needs, depending on species, but most need soil that is consistently moist. For spring bulbs, except in the case of a very dry spring, irrigation is not usually needed until about the time flower buds appear on the plants. Once started, irrigation will likely be needed until the foliage dies and the bulbs go dormant. Because they are planted deep, bulbs should be irrigated less often and to a greater depth than nearby lawn areas. Summer flowering bulbs will likely need water until first frost.


Bulbs are not considered heavy feeders, but do need an annual application of fertilizer to look their best. Use a complete fertilizer that is relatively high in phosphorus. Apply the equivalent of 2-3 lb nitrogen per 1,000 sq.ft. Timing of application is fairly critical. Bulbs begin growing new roots very early in the spring and need fertility available to start this process. So, the best time to apply fertilizer to spring bulbs is in October or early November. A second option is to apply half the fertilizer in the fall and the other half about the time the plants begin to flower. Summer blooming bulbs do best with fertilizer applied about the time the plants emerge or when they are transplanted outside.

Weed Control

There are no options to completely replace hand weeding in bulbs. Mulching with organic matter or weed barriers will help by blocking germination and growth of weed seed. Perennial weeds that emerge before the bulbs can be sprayed out with a glyphosate product. Grasses in irises and gladiolas can be controlled with a grass herbicide containing sethoxydim. Grass controlling herbicides cannot be used on other bulbs without risk of serious injury.


Some bulb plants, especially summer bulbs, have large flowers and somewhat weak stems. They may need to be tied to stakes or allowed to grow inside a support cage to remain upright and attractive.


Foliage should die naturally before pruning

Post-bloom Care

Immediately after the bloom period, all seed heads should be removed. This not only improves appearance, but allows the plant to direct its energy to producing new and larger bulbs. The foliage of bulb plants should be allowed to die naturally (or at least be yellow and dying before removal). Healthy leaves are essential to the process of growing new bulbs. Over a period of a few years, removing the leaves too early will cause the bulbs to become smaller and decline in vigor.

Many gardeners do not like the look of post-bloom foliage in the garden. The unattractive leaves can be masked by planting other types of flowers in the bulb garden that will take up the slack in bloom time while the bulbs complete their growth and decline.

Over a period of several years, some bulb plants, such as daffodils, tulips, and crocuses will produce many bulbs and become crowded. When severe, this crowding will reduce bloom potential and make blooms smaller. This can be solved by uncovering the bulbs, dividing them into single units, and replanting the largest and healthiest of the bulbs at a more appropriate spacing. Dividing is best done in the fall, the usual time for planting bulbs. However, by fall all sign of foliage is gone and it is hard to identify the location of the bulbs. This can be solved by using small stakes to mark the plants before they die, or as a second best option, by simply dividing in late spring when the foliage has declined but still marks the presence of plants. Bulbs that are freshly dug and divided should be replanted as quickly as possible to prevent damage from drying conditions. Although not considered an option of choice in Idaho , spring bulbs can be harvested after blooming and stored in the refrigerator until being replanted in the fall.

Tender summer bulbs

Tender summer bulbs must be harvested and stored in the fall

In all regions of Idaho , the tender summer bulbs, such as dahlia, canna, tuberous begonia, and gladiolas must be harvested at the end of the growing season and stored indoors. Otherwise, the bulbs will be damaged or killed by freezing soil conditions. At the first sign of frost injury on the foliage, the bulbs should be harvested, cleaned, cured, and stored. Proper storage conditions vary by species. Complete discussion of the harvesting and storing process, including proper storage conditions for common summer bulb plants, can be found in a University of Minnesota document written by Mary Meyer.

The University of Illinois provides more general information on growing bulbs.

Forcing Bulbs

The term forcing refers to growing practices that bring bulb flowers into bloom during the off-season. Typically, this process is used to produce indoor flowers during the winter months. For each species, certain environmental constraints must be met to overcome bulb dormancy and allow growth and bloom. For spring bulbs, this usually means cold storage before planting in a pot. For summer bulbs, it may mean supplying specific requirements of light duration. It is beyond the scope of this discussion to provide specific requirements of all plants, but understand it can be done and seek procedures elsewhere. Information on forcing spring bulbs can be found on the University of Kentucky site.

Insect and Disease Control

It is beyond the scope of this site to provide specific pest management information for the large number of commercially available bulb species. Each has unique problems that may be more or less serious. However, there are many pests that are common and infest many types of plants. Diagnostic and simple control information will be given below for these common pests. For detailed information on control of insects and diseases, as well as information of other pests, see the Insect and Disease Pests section of this site.

Insect Problems

Aphids: Also known as plant lice. Small, soft-bodied, sucking insects that cluster on the stems or underside of leaves. Aphids are usually wingless and green, brown, or black in color. Symptoms of infested plants include distorted or curled leaves, presence of sticky sap (honeydew) on the infested surfaces, and misshapen new growth.

Aphids can be controlled with the use of insecticidal soap or a registered insecticide. A strong stream of water directed at the infected plants may knock them from the plant. Many beneficial insects feed on aphids and if an infestation is not too severe, it may be appropriate to be patient and let nature take its course.

Spider Mites: Not actually insects, these miniscule pests are actually related to spiders. They spin protective webs on the underside of leaves and feed by sucking juice from the leaves. Symptoms include color mottling that, at a distance, may appear as a general yellowing of older leaves. Webbing will be presence on the underside of infested leaves. The mites, to small to be easily visible, can be detected by shaking a leaf over piece of clean white paper.

Spider mites prefer dry, dusty environments. Sprinkler irrigation or routine washing of leaves with water usually keep them at bay. A severe infestation may require the use of a registered miticide. Most common insecticides are ineffective against spider mites.


Slugs can damage many bulb flowers

Slugs and Snails: Prefer damp soil and humid conditions. Slugs and snails often hide during the day and feed at night. Symptoms include chewed leafs and glistening slime trails on plant surfaces.

Control snails and slugs with baits.

Thrips: Damage is cause by the larva of this small, four-winged insect. Thrips reside on the underside of leaves and use their rasping mouthparts to scrape away the surface of the leaf after which they feed on the sap. Symptoms appear as white streaks and blotches, more prominent on the underside of the leaf.

A light infestation does little permanent damage to the plant and can be ignored. A heavy infestation will likely require the use of a registered insecticide.

Disease Problems

Root and Bulb Rots: Are caused by the penicillium (blue mold) and Fusarium fungi and the soft rot bacteria that live in the soil. These organisms are worse problems on bulbs that are harvested and stored than on those that are left in the soil over winter. Infected bulbs become soft, pink, or mushy and often have an offensive odor.

Control measures include careful harvesting to prevent injury that provides a point of entry for rot organisms. Infected bulbs should immediately be eliminated.

grey mold on peonies

Grey Mold affects many bulb plants, including peony

Grey Mold or Botrytis: Is caused by a fungus that overwinters in the soil. It infects plant stems that touch moist soil surfaces and splashed onto leafs with rain or irrigation water. Symptoms include water-soaked spots on the leaves that become a slimy, grey mold. Infected tissue quickly collapses and dies.

Control includes removal of infected tissue, both live and dead. In severe cases it may be necessary to apply a preventative fungicide.

Daffodils with virus

Bulb can be affected by chronic viruses

Virus: Not technically alive, viruses are small, disruptive pieces of genetic material that disrupt plant function. Symptoms vary widely and usually include some combination of stunting, yellowing, mottling, or leaf and stem distortion. Viruses are a particularly severe problem on bulbs and other perennials because their long life span and lack of seed propagation create many opportunities for chronic infection.

There are no control measures for viruses other than using resistant varieties or controlling the organisms (usually insects) that transfer them from one plant to another. Prevention involves removing and destroying any infected plants.

Information on control of garden insects and diseases common to Idaho can be found in the online Idaho Master Gardener Handbook.

See specific information on controlling bulb diseases and insects at the University of Connecticut web site.


Ornamental onions

Ornamental onions are eye-catching summer bulbs

 August 17, 2012
Aug 162012

Billbugs are perhaps the most common insect affecting home lawns in Idaho. The adults, which are about 1/4 inch long, can be seen in the spring, walking along sidewalks especially on the southern sides of buildings.

Adult bluegrass billbug

Adult bluegrass billbug crawling on a sidewalk. (Photo courtesy: H.D. Niemczyk, Ohio State University)

The adults are a black weevil, have a long snout and will play dead when disturbed. The adults do very little damage, but in the larval stage billbugs eat grass stems and roots. Adults become active when soil temperatures reach 55º F, usually early to mid-May. The larvae are small (1/8 – 1/4 inch long), white, legless grubs with a brown head.

Billbug Larva and adult.

Billbug Larva (right) and adult. (Photo courtesy: H.D. Niemczyk, Ohio State University)

Lawns damaged by billbugs look like they are drought stressed because the grass blades are basically severed from the roots. Grass blades can be easily pulled out by hand with a light tug. A healthy, vigorously growing lawn will recover from moderate billbug damage and symptoms may go unnoticed. However, under-fertilized lawns or lawns that are otherwise stressed will be more susceptible to billbug damage.

Control. If you have areas with known billbug problems, control measures should be targeted against the adults in the spring when they are active and seen crawling along sidewalks or other exposed areas. Waiting until damage is visible may be too late since the damage has already been done. If targeting larvae, good coverage and movement of the insecticide past the thatch layer are very important. Since adults are on the surface of the turf, they are more easily contacted with insecticides.

 August 16, 2012
Aug 162012

White grubs are the larval stage of a beetle known as scarab beetles or more commonly as May/June beetles and masked chafers. White grubs have a characteristic “C” shape, are creamy white, with three pairs of legs and grow to a size of up to 1 to 1¼ inches long.

White grubs

White grubs in grass root zone. (Photo courtesy: A.J. Koski, Colorado State University)

White grubs feed on grass roots causing severe wilting and eventually death of affected lawns. The sod will tend to lift away when pulled, but grass blades will generally stay intact since the grubs have mainly eaten roots. Additionally, skunks and raccoons in search of larvae will cause considerable damage as a result of their digging and feeding on grubs.

Grubs are generally found in the top inch or so of the soil and will go much deeper during the winter months. Masked chafer grubs have a one-year life cycle overwintering as larvae with the adults emerging in mid to late June.

The May/June beetles on the other hand have a three-year life cycle with adults emerging in May and June, laying eggs and the larvae feeding during the summer and overwintering. The second year, when most of the damage occurs, the grubs feed throughout the summer. In the third year, the grubs complete their development in the spring and early summer forming pupae and adults the following year to start the cycle again.

Control. Many insecticides are labeled for white grub control, however, it is very difficult to control white grubs because of the difficulty of getting the chemical into the soil where they are active. Excessive thatch can impede the movement of the chemical into the root zone where grubs are feeding. Core aeration can help increase the effectiveness of insecticide applications. Proper watering will also help, but it is important not to ove- water. Over-watering can actually decrease the effectiveness of insecticides.

Find additional information on billbugs and white grubs at Colorado State University.

 August 16, 2012
Aug 162012

Earthworms and night crawlers are the main cause of bumpy lawns, a common complaint of many homeowners. Worms leave castings or small mounds of soil on the soil surface. These mounds soon dry and harden causing an uneven surface, which can be somewhat bothersome during mowing operations. It is important to remember that the benefits of earthworms far outweigh the nuisance caused by these castings. Earthworms help decompose thatch, improve water and air movement and soil structure for good root growth. Earthworms are indeed a good indicator of a fertile soil.

Extremely bumpy lawns may also indicate other problems such as a thin turf stand due to a poor fertilization program. Following good fertility and watering guidelines will keep a lawn growing vigorously and will make bumps less noticeable.

In severely bumpy lawns, rolling in conjunction with aerifying may help reduce the problem, but generally, lawn rolling is not advised since it can lead to soil compaction.

 August 16, 2012
Aug 132012
University of Idaho


Encouraging Beneficial Insects in Your Garden
2001 PNW 550 Price: $1.00 (available in hardcopy only)

Honeysuckle Witches’ Broom Aphid
1992 CIS 956 Price: $0.75 (available in hardcopy only)

Locust Borer, The
1988 CIS 829 Price: $0.25 (available in hardcopy only)


Bacterial Wetwood and Slime Flux of Trees
1990 CIS 876 Price: $0.25 (available in hardcopy only)

Cytospora Canker Disease in Idaho Orchards
1984 CIS 726 Price: $0.25 (available in hardcopy only)

Diplodia Tip Blight on Ponderosa Pine
1992 CIS 946 Price: $0.50 (available in hardcopy only)

Phytophthora Collar-Rot of Orchard Trees
1985 CIS 752 Price: $0.50 (available in hardcopy only)

Management of White Pine Weevil in Spruce


Controlling Iron Deficiency in Plants in Idaho

Controlling Sunscald on Trees and Shrubs
1990 CIS 869 Price: $0.25 (available in hardcopy only)

Nutrient Disorders in Tree Fruits


Why Home Fruit Trees Die
1986 CIS 776 Price: $0.25 (available in hardcopy only)

University of Illinois

Cytospora Canker of Spruce
Needle Cast of Spruce
Spruce Spider Mite
Sphaeropsis (Diplodia) Blight

Pine Wilt
Pine Diseases Chart
Phomopsis Blight of Juniper

Cedar Rust Diseases
Phomopsis Tip Blight
Kabatina Tip Blight
Cercospora Blight
Pestalotiopsis Blight
European Pine Shoot Moth & Nantucket Pine Tip Moth
Zimmerman Pine Moth
Yellow Belly Sapsucker
Pine Bark Adelgids
Pine Needle Scale
Pine Tortoise Scale
Pales Weevil, Root Collar Weevil, Root Collar Weevil
Pitch Mass Borer
Gypsy Moth
Spruce Mite
Spruce Gall Adelgids
Spruce Needle Miners
Spruce Bud Scale
Apple Scab
Black Knot
Cedar Apple Rust
Cedar Hawthorn Rust
Cedar Quince Rust
Crown Gall
Gray Mold
Oak Wilt
Powdery Mildew
Verticillium Wilt

Ohio State University

Anthracnose Leaf Blight of Shade Trees
Cedar Rust Diseases of Ornamental Plants
Control of Phytophthora and Other Major Diseases of Ericaceous Plants
Cytospora Canker of Spruce
Diseases of Ground Cover Plants
Disorders of Yew (Taxus) in Ohio
Girdling Roots — A Problem of Shade Trees
Leaf Diseases on Ornamental Trees and Shrubs
Oak Wilt
Powdery Mildews on Ornamental Plants
Rhizosphaera Needlecast on Spruce
Root Problems on Plants in the Garden and Landscape
Sooty Molds on Trees and Shrubs
Verticillium Wilt of Landscape Trees and Shrubs
Yellowing, Dieback and Death of Narrow-Leafed Evergreens

University of Vermont
Pest Management
University of Massachusetts

Helping Trees Recover from Stress

University of Minnesota

Garden: Trees & Shrubs – Insects/Diseases

Ohio State University


 August 13, 2012
Aug 132012

Plant Problem (Symptoms) Pathogen Insect Physiological Notes
Plant stunted, weak growth, leaves off color or limbs dying Powdery mildew (white powdery fungus on leaves), rusts (red, black or orange spots on leaves), leaf spot (black spots on leaves borer damage to stem or leaves, look for holes in stems or leaves Poor soil drainage, drought damage, excess soil drainage, planting too deeply, improper soil pH, cold damage, lawn mower damage, sunscald, stem breakage, animal damage Consider working organic matter into soil before planting shrubs or trees to help improve soil aeration and water-holding capacity. Lack of water is the primary cause of death to recently transplanted shrubs and trees
Plants dying suddenly Root rots (fungus) Insect larva attacking roots Over fertilizing, severe drought damage, poor soil preparation When root rot damage is moderate, symptoms may be similar to those of drought damage
Yellowing (chlorosis) Viruses may cause a mottled appearance on the leaves Insect damage to stem or stippling of leaves Nutritional deficiency (N, Zn or Fe), poorly drained soil, over fertilization, mechanical damage to stem N deficiencies occur on lower leaves first and move up the plant. Fe deficiencies result in interveinal chlorosis of the upper leaves first.
Browning of margin or edges of leaves Root rot (fungus) Frost or cold damage, drought damage, transplanting shock, poor soil drainage, excessive fertilization, mechanical damage Frost damage usually occurs in early spring as buds leaf out. Damage may not be visible for a month or more.
Plant fails to flower Bud blight and other fungal diseases of the flowers Aphids, thrips, grasshoppers, and other chewing or sucking insects Plant is too young or excessive vegetative growth over shading High N levels in soils and ideal growing conditions may delay flowering of some plants.
Plant fails to produce berries Fungal diseases at flowering Cold or frost during flowering, plant is a male or a male plant is missing with only female plants present, improper pruning Using hedge shears to prune shrubs usually results in the removal of most of the tip growth and future flower buds. Berry-producing plants are best pruned by removal of individual limbs inside the plant.
Loss of berries before maturity Fungus disease on berries insect larva Drought damage In mild to moderate attacks by floral diseases, the berries may be discolored or deformed.

Taken from: Perennial Ornamental Plants. H.S. Fenwick, Extension Plant Pathologist. University of Idaho College of Agriculture. Current information Series 146, 1977.

 August 13, 2012
Aug 102012

Insects should be controlled only when they appear in numbers large enough to be destructive. There are five simple strategies for managing insects in a vegetable garden, effective in either traditional or organic systems.

Clean Up

Be a sanitary gardener. Insects will often overwinter in old garden refuse, so it pays to clean up dead plant material at the end of the year. If you want to keep the organic matter in the soil, till or plow the garden after the last of the crops are harvested.

Plant Care

Maintain good plant health. Healthy plants can often partially defend themselves from pests and will recover from damage quicker.

Physical Control Methods

Use physical barriers and cultural controls. You can keep some types of insects at bay by preventing access to the plants. For example, collars around the lower stems of small plants will foil cutworms.

Biocontrol and IPM

Encourage or release beneficial insects. Encourage the presence of predator insects by allowing the presence of a low level of pest (prey) insects and by avoiding the use of broad-spectrum (kills all insects) insecticides in the garden.

Pesticides Use

Judiciously use pesticides as a last line of defense. For many insects, both organic and synthetic insecticide options are available. If insecticides are used, direct the application to the specific problem rather than broadcast an application across the garden. Also, use products that target the specific insect you are trying to control. Make an effort to identify and use the most ecologically friendly products available. All insecticides are not equal for either efficacy or impact.

Insects that commonly infest Idaho gardens at damaging levels
  • Aphids: These stem and leaf feeders can often be controlled without the use of insecticides. Insecticidal soaps or a hard stream of water that simply knocks them off the plant will usually be sufficient to eliminate damage. Also, aphids will almost always be eliminated by predators if you are patient enough to let them do their work.
  • Grubs and Wireworms: These soil-dwellers are difficult to control and may require the use of a soil-applied insecticide prior to planting. This means knowing the history of the garden plot and realizing the problem exists before you see damage.
  • Cutworms: This pest often kills seedlings and transplants by chewing through the stems at ground level. Cabbage, broccoli, tomatoes and other soft-stemmed transplants are often the victims. Placing cardboard collars around the base of plants is an effective method to prevent damage.
  • Corn Earworm: Control of this pest usually requires the use of an organic or synthetic insecticide product, applied to the green silks once or twice.
  • Slugs: In dry climates, slugs and snails are typically not a problem unless too much water is being applied to the garden. If the problem cannot be solved by reducing irrigation, the use of baits and traps can be partially effective.
  • Cabbage Worms: These slender green caterpillars chew holes and deposit webs on broccoli, cabbage, cauliflower, and kale. When obvious damage is present, they may require control with bacillus (the organic pesticide sold as Bt) or another insecticide.
  • Tomato Hornworms: These large, ferocious-looking caterpillars can defoliate tomato or potato plants within a day or two. Physical control (pick them off the plants and step on them or squeeze them between two rocks) is the best method for eliminating this occasional pest
  • Colorado Potato Beetles: These serious pests of potatoes, when present is small numbers, can be removed from the plants by hand. In large numbers they may require an insecticide.

To learn more about controlling vegetable insects, see the following resources:

From Cornell University: Managing Home Garden Vegetable Pests
From Oklahoma State University (very detailed): Home Vegetable Garden Insect Pest Control
From Organic Garden Pests.com (for tips on organic control of insects): Organic Pest Control

 August 10, 2012
Aug 102012

Currants, gooseberries, and jostaberries are quite easy to grow in Idaho. These fruits in the genus Ribes were once grown commercially in the United States and Canada. All of them, particularly black currants, are grown in Europe and New Zealand today. American fruit growers are also once more considering currants and gooseberries for commercial production.

Currant and gooseberry production, particularly black currants, has largely been restricted in the United States because these crops can serve as alternate hosts of white pine blister rust, which has caused major problems for the timber industry. At one time, efforts were even made to eradicate all domestic and native gooseberries and currants in the country. Although these eradication efforts failed, the development of new selections of blister rust resistant white pine, currants, and gooseberries has reduced the problems associated with the disease, and restrictions on Ribes cultivation are being relaxed. There are currently no restrictions on growing currants or gooseberries in Idaho.

Download our free how-to guides!
Growing Currants, Gooseberries and Jostaberries in the Inland Northwest and Intermountain West

All Currants and Gooseberries

Cold hardiness: 20 to -31 F
Optimal pH: 5.8 to 6.8

Black Currants

Expected yield: 5 pounds per bush
Age to maturity: 3 to 4 years
Productive life: 15 years or more
Spacing: 8 to 10 feet apart 4 to 5 feet apart in rows

Red and White Currants

Expected yield: 5 to 8 pounds per bush
Age to maturity: 3 to 4 years
Productive life: 15 to 20 years or more
Spacing: 8 to 10 feet apart 4 to 5 feet apart in rows


Expected yield: 5 pounds per bush
Age to maturity: 4 to 5 years
Productive life: 15 to 20 years or more
Spacing: 8 to 10 feet apart 4 to 5 feet apart in rows

Red and white currants are genetically the same, differing only in fruit color. These colorful, tart fruits can be eaten fresh, make excellent jellies and syrups, and brighten up dishes when used as garnishes. Black currants were developed from different species and lack the bright, translucent skins of their red and white cousins. Except for the American black currant variety ‘Crandall,’ black currants have a strong flavor that makes them best suited for processing into jellies, syrups, and other foods. Black currant juices and drinks are rich in vitamin C and other beneficial compounds, and are tremendously popular in Europe. Black currants are also rich in anthocyanins, phenolic acids, and antioxidant capacity, making them particularly healthy additions to the home garden.

Currants are noted for their cold hardiness. You can grow them successfully in USDA Plant Hardiness Zones 3b to 7.

Gooseberries range from white to yellow to green to red in color and vary in size, from small marbles to plum-sized fruits. They resemble grapes in appearance and flavor, and make good substitutes in the garden in locations too cold for grape production.

Jostaberries are hybrids between gooseberries and black currants. The very vigorous, thorn-free canes bear dark purple fruits about the size of medium-sized marbles. The fruits lack the strong black currant flavor and can be used fresh or processed.

Selecting a Site

Ribes are adapted to cool, moist conditions and are noted for their cold hardiness. They do not, however, tolerate high temperatures well, especially when combined with intense sunlight. They can be grown in partial shade, but yields are better in full sun. For reliable fruit production, your site should have 120 to 140 or more frost-free days. Mountain and valley locations in northern and central Idaho are excellent for currants. High temperatures combined with intense sunlight and droughty, alkaline soils can make production difficult in parts of southeastern and southwestern Idaho. In these areas, consider growing currants, gooseberries, and jostaberries in partial shade, preferably screened from the afternoon sun.

Ribes grow best on deep, organic-rich, well-drained soils with good water-holding capacity and a pH of 5.8 to 6.8. They tolerate heavier soils and poorer drainage than raspberries, blackberries, or blueberries, although they grow and produce better when the soils are well drained. On heavy soils, alkaline soils, or poorly drained sites, grow these crops in raised beds at least twelve inches high and three to four feet wide.

Pests and Diseases

Several pests and diseases can make Ribes production challenging in Idaho. Powdery mildew damages stems, leaves, and fruits, and can kill highly susceptible plants. In general, European gooseberries are the most susceptible Ribes crop, followed by black currants and red and white currants. Jostaberries are quite resistant to powdery mildew. Starting in early spring just as the new leaves are emerging, applications of sulfur sprays every two weeks can help control powdery mildew. Stylet crop oil can also help control mildew. Dormant applications of lime sulfur and/or Bordeaux fungicides help control the disease, as does raking up and disposing of leaves and prunings. By far the most effective strategy is to select varieties that are resistant to powdery mildew.

Avoid problems with white pine blister rust by planting resistant varieties. If you live within one mile of native or ornamental five-needled pines, plant only varieties known to be resistant to blister rust. For information on controlling currant and gooseberry diseases, click here.

Several pests can seriously damage currants, gooseberries, and jostaberries if left unmanaged. Imported currant worm, currant fruit fly, and various stem borers are the most common and serious pests. For information on identifying and controlling these pests, click here.


Red and white currants are generally considered self-fruitful, but can benefit from cross pollination on some sites and in some years. For reliable production, plant two red or white currant varieties together. White and red varieties can pollinate one another. Black currants are at least partially self-sterile and you should plant two varieties close together to ensure good fruit set. For black currants, the variety ‘Titania’ is the best blister rust-resistant variety available in the United States. Use ‘Consort,’ ‘Coronet,’ or ‘Crusader’ black currants as cross pollinators.

Because they are highly susceptible to powdery mildew, European gooseberries can be very challenging to grow in Idaho. American varieties, although generally producing smaller fruits, are much easier and more reliable to grow here.

Only a few jostaberry varieties are available. ‘Josta’ is the most common. Other varieties include ‘Jostaki’ and ‘Jostagrande (a.k.a ‘Jogrande’). The latter two should be planted together to ensure cross pollination. Josta is partially self-fruitful and can be grown alone.


Most currants, gooseberries, and jostaberries are pruned while they are dormant during the late winter and early spring, but you can prune any time after the leaves have dropped in the fall. Fall pruning improves air circulation around bushes during wet fall, winter, and spring months, and can decrease disease problems. Remove unwanted canes as close to the ground as possible, and always remove drooping canes that lie close to the ground. Canes are normally not shortened or headed back. Be careful while pruning red currants, white currants, and gooseberries not to damage the spurs. Most of the fruit for these crops is borne on short spurs on two and three-year old canes. Black currants bear most of their crop at the base of one-year-old shoots and spurs on two-year-old wood.

With mature red and white currant, gooseberry, and jostaberry bushes, your goal should be to keep three or four strong, new canes per plant each year, and to remove an equal number of the oldest canes. In this system, mature plants have nine to twelve canes after pruning, three to four each of one-, two-, and three-year-old wood. Remove all wood that is four years old or older.

Black currants are more vigorous than other currants and gooseberries, and you normally leave more canes. As a general rule, leave ten to twelve vigorous canes per bush. If the bushes are very vigorous, leave a few more canes. About half of the canes left after pruning should be one-year-old, with the remaining half being vigorous two-year-old canes. Remove all canes that are more than two years old.

Weed Control

Mulch your plants to provide weed control. Four inches of sawdust mulch around currants and gooseberries helps control annual weeds, maintain soil moisture, and keep soils cool. Rake mulches away from plants in early spring to allow the soil to dry and warm. Cold, wet soils retard plant growth. Ensure that quackgrass and any other perennial weeds are eradicated before applying mulch.

 August 10, 2012
Aug 102012

The most important tool in managing pests and diseases in your orchard is regular scouting. At least weekly, closely examine the trunks and branches, flowers, leaves, and fruit for signs of pests or diseases. If you are not sure what a problem is or how to control it, get help from your county extension office, nursery or garden center.

Just as the buds are swelling, but before they open in early spring, you may wish to apply a spray of dormant crop oil. Even better is a mix of dormant oil and sulfur. The oil helps control pests by smothering the overwintering pests and eggs. Beneficial insects and mites that feed on these pests usually overwinter elsewhere and are not harmed by the oil. Various sulfur formulations are available to gardeners for dormant applications are very valuable in helping manage fungal diseases. Your garden center can advise you on suitable products. Always follow label directions and regulations carefully. Some dormant oils and sulfur treatments are approved for organic fruit production.

 August 10, 2012
Aug 092012

Inspecting a treeAbout this time of year, I begin to experience what I call “garden itch”. I really want to get out and dig in the dirt and make something grow. Garden books tell us winter is the time to study garden catalogues, complete seed orders, and make plans for the next spring. While fun, these activities don’t seem to satisfy my itch.

However, all is not lost. There is one important gardening activity that is best completed in the winter. It involves conducting a thorough tree inspection. This is especially effective for deciduous trees because they no longer have leaves to hide their problems. So, on a sunny winter day, put on your hat and boots and take a close look at your trees.

What to look for:

Although winter may not be the time you want to solve tree problems, it is the time to identify them. Here is a list of things you may want to look for.

Inspecting a treeStructural Problems: look for situations that can be early signs of weakness that may later lead to branch or tree failure. Many of these can be solved later on through judicious pruning. Specifically, look for branches with a poor attachment angle. Where they join the trunk, branches should be directed slightly upward at an angle of 45 to 60 degrees. If they are too horizontal, or too upright, they will become weak. Plan to remove such problem branches, if it can be done without destroying the structure of the tree.

Inspecting a treeAlso, look for cracks and splitting around branch junctions. If you find such damage on large trees, you may need to access some professional help to determine the best action. On small trees, you can reshape the tree to relieve the pressure that is causing the problem and help the tree heal itself. The last thing to look for is something called included bark. This is a situation where the tree does not make normal wood on the top of the branch junction and instead produces bark in the joint. It can be recognized by the soft, corky tissue (it may create an open crevice or be closed) that is present on top and down into the branch union. This makes the branch very weak. It is often associated with a steep branch angle. Plan to remove these weak branches if feasible.

Inspecting a treeArchitecture and Appearance: When the tree is bare, you can step back and look at its overall growth habit. Determine whether or not it has good balance and overall appearance. Decide if the crown needs to be raised, lowered, or cleaned (but never topped). Record a pruning plan that can be implemented in the spring to improve the tree’s appearance and functionality.

Pests and Disease Problems: Although pests are typically not damaging during the winter, it is still a good time to look for problems that can be addressed during spring or summer. Some of the most destructive insect pests on trees are borers. Look for the small holes, the sawdust-like frass, or loosened bark that may indicate a problem is looming. Other types of insects such as aphids or beetles will overwinter as eggs on the trees and may become problematic next summer. Do some homework before the inspection and find out what to look for based on common problems for the tree species you are inspecting. Also, check for disease problems that appear as cankers on the bark. If you find such problems, study up on the solutions and prepare to deal with them when the season is right. That will give you one more scratch for the gardening itch.

A good winter tree inspection will identify problems you may not know you have. It will also give you time to come up with a good solution to one or more of the many issues that affect tree health. Winter may be a slow time for garden chores, but it does not need to be unproductive.

—Stephen Love, Consumer Horticulture Specialist

 August 9, 2012
Aug 092012

Pesticides are an effective tool for combating numerous problems encountered in the home landscape and garden. When used properly they can save time and labor. Used improperly, however, pesticides can cause damage to plants, people and the environment. It is very important to read and understand the label on any pesticide container. In fact, the label is the law. Keep in mind that all pesticides are potentially poisonous and that improper application or use can be dangerous.

Warning Pesticide Use signThere are several categories of pesticides, and numerous products, available for use in the home garden. Herbicides can be used to control weeds. Some products will kill all vegetation and should be used only where no desirable plants reside. There are a small number of these products that sterilize the soil and prevent growth of any plants for several years. Products that sterilize the soil may also damage nearby trees and shrubs if the roots grow into or are already located in the treated area. Be sure you understand the nature and limitations of any compound applied. Some herbicides can kill seeds as they germinate but do not affect growing plants that are already growing. These can be used to control weeds around shrubs, trees or emerged garden plants. Other herbicides kill only certain types of plants, such as grasses. These can be used to control grass weeds in broadleaf garden plots, or their opposite counterparts can be used to control broadleaf weeds, such as dandelion, in lawns. In a garden, herbicides can make weed management easier, but cannot completely replace hand weeding.

The intended use of insecticides is to kill destructive insects and are often very important for managing garden pests. However, because these compounds are designed to kill animal pests, they are often the most toxic and damaging to the environment of all classes of pesticides. Insecticides can also kill beneficial insects so it is again important to read the label to avoid killing insects that help you out in the war against damaging insects. Insecticides should be used only when needed and then only when using all appropriate precautions.

Fungicides and bactericides are used to control plant diseases and can save your lawn, garden, and landscape plants from disease when applied in a timely manner. For many diseases, fungicides must be applied to the target plants before the disease appears. Consequently, they are often used in a preventative fashion.

For further information on pesticides, please refer to the following links:

For detailed general information on controlling pests in gardens, see chapters 9 – 14 in the Idaho Master Gardener’s Handbook.

For general instruction on reading labels and using pesticides in the home garden, see the following informative University of Idaho publication: Pesticides for the Home Garden and How to Use Them

See the EPA document Citizen’s Guide to Pest Control and Pesticide Safety for a comprehensive treatment of pesticide selection, management, and safety.

View a comprehensive database of pesticide products for home use from the Household Products site.

Purdue University has published A Strategy for Pest Control in Home Gardens outlining non-pesticide strategies for pest control.

For information on storing and disposing of pesticides, follow this link to an informative University of Idaho publication, Idaho Homeowner’s Commonsense Guide to Pesticides.

 August 9, 2012
Aug 062012

Gardeners like to improve their soils, and often do so by adding composts, manures, straw, sawdust, or other organic materials. There are both benefits and risks associated with soil amendments. Perhaps the greatest advantages to organic soil amendments are that they can increase water and nutrient holding capacities on light-textured soils and can be sources of plant nutrients.

Amendments also carry risks. Weeds, pests, and diseases can easily be brought into your garden through contaminated organic materials. Woody materials, such as straw, bark, and sawdust, can create severe nitrogen deficiencies in the soil as they decompose. Woody materials are broken down by microorganisms in the soil. These microorganisms take nitrogen from the soil to use for proteins and other compounds in their bodies. Until the woody material is decomposed and the microorganisms die, the nitrogen is unavailable to plants. An excellent strategy to avoid importing weeds, pests, and diseases and to avoid depleting your soil nitrogen is to thoroughly compost organic amendments before adding them to your garden.

Learn more about composting here.

 August 6, 2012