UI Extension Master Gardeners UI Extension Events UI Extension Idaho Landscapes and Gardens Seasonal Topics UI Extension Idaho Landscapes and Gardens Get Answers UI Extension Idaho Landscapes and Gardens UI Extension Idaho's Growing Regions University of Idaho Extension UI Extension Idaho Landscapes and Gardens UI Extension Idaho Landscapes and Gardens Image Map
Aug 202012
desert landscaping

Photo courtesy of Desert Water Agency

There is a positive trend toward  utilization of native plants in Idaho home and business landscapes. The goals of this type of landscaping are myriad, including water conservation, reduced maintenance, attraction of wildlife, uniqueness, and expression of personal creativity. Regardless of the reasons, native landscapes can be beautiful and effective if designed and completed properly. Here are some guidelines that will help you successfully design and establish a native landscape. They closely resemble the steps for establishing a traditional landscape, but differ in a few important aspects such as plant materials and maintenance planning.

  1. Complete a yard survey and map the existing landscape. Note problem areas that are difficult to manage and may be appropriate for native landscapes.
  2. Determine the areas to be planted using native or water conservation materials. It is not necessary or desirable to make an entire landscape native. Some areas should be more traditional with good shade, turf for recreation, leisure areas, and flower beds for consistent color. However, the location of native plantings will determine much of the design. Areas removed from public scrutiny, such as property corners and large back yards, can remain informal and will have less demand for maintenance. Native plantings in public areas, such as around the house entrance, can be as pleasing as traditional landscapes, but will require a more elaborate design.
  3. Design the native planting areas in such a way that they provide continuity and flow with the rest of the landscape. Zone the irrigation system to meet the needs of the native plants. Some areas may need less water if xeriscape principles are followed, while other areas (such as water features and lowland plantings) may actually need more water. Recognize that if a native planting is designed for low water use, it may be necessary to add landscape features other than plants, such as rocks or wood objects to maintain season-long interest, color, and texture.
  4. Choose plant materials that will provide balance, color, line, and movement and complement the rest of the landscape while at the same time meeting the goals of the design. Carefully consider transition zones between traditional and native components of the landscape and avoid sudden shifts in plant type. Carefully consider the mature size of all plant materials and arrange plantings accordingly. Do not mix plants with vastly different water or maintenance needs.
  5. Once the design is complete, install the new landscape using procedures outlined in the section above. In the case of a water-conserving landscape, remember that newly established plants are not especially drought tolerant for the first season and may need some supplemental water for several months.

There are some outstanding publications available on-line that provide detailed instructions for establishing a native landscape. Here are a few of the best that are appropriate for Idaho:

Utah State University provides an excellent instruction manual for planning, designing, and establishing native plant landscape.

r. Stephen Love, University of Idaho, has created a list of native plants that are suitable for landscaping in Idaho. Included in his document is contact information on where to purchase the listed plants. This document  is periodically updated.

The Bureau of Land Management published and internet document entitled, Landscaping with Native Plants of the Intermountain Region. It serves as an excellent native plant selection guide, complete with pictures, and also contains information about sources for native plants.

Several photographs utilized in this discussion of landscaping were supplied courtesy of Gizmo Creations, LLC, Merrifeld, Minnesota.

 August 20, 2012
Aug 172012

Experts agree that only a very small percentage of the insects and spiders in our yards and gardens are actually pests, feeding on our desirable vegetation or infecting it with plant diseases. Indeed, many insects are helpful partners in our gardens, devouring aphids and other plant-eating pests. Pollinators like honeybees and butterflies are essential participants in the reproduction of many flowers, fruits, and vegetables. Some small, stingless wasps or flies assist us by laying their parasitizing young on or inside doomed pests. Although beneficial insects won’t keep our yards pest-free, their contributions should not be underestimated.

Helpful links:

Biological Control: A Guide to Natural Enemies in North America, Cornell University

IPM Online, University of California

caterpillarHelping beneficial insects feel at home

As a gardener, there are things you can do to help sustain natural populations of beneficial insects:

Provide their preferred and alternative foods – Scatter a wide assortment of flowering plants throughout your garden and landscape or cluster them in a designated bed or border. Because different beneficial insects use pollen and nectar at different times, choose diverse plants with long, overlapping bloom periods. Pollinators aren’t the only beneficials that rely on flowering plants. Nectar can help parasitoids (insects that develop in or on another insect pest) span periods when hosts are few. Nectar, pollen, and plant juices can also help predators (insects such as ladybird beetle larvae, above,  that consume other harmful insects) survive times when prey numbers are low.

Provide shelter – Beneficial insects need protection from predators and human disturbances. These beneficial insects can find cover in perennial flower beds, hedgerows, cover crops, and mulches.

Provide water - Bird baths, shallow containers, or temporary puddles, with sticks or rocks for perching, can help beneficial insects through dry periods. Change the water every two or three days to discourage mosquito breeding.

Protect them from insecticides - Broad-spectrum insecticides kill beneficial insects right along with pests. To minimize impacts on beneficial insects, choose chemicals that are less toxic and more specific. Consider these environmentally “softer” alternatives: insecticidal soaps, horticultural oils, botanicals, Bacillus thuringiensis (Bt), and insecticidal products that act specifically as stomach poisons to foliage-feeding pests.

 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
blue fescue

Fescues add texture to naturalized plantings. Photo courtesy of Judy Sedbrook

Water Conserving Landscapes

These grasses require little care and minimal water after establishment to remain attractive. They are generally drought and heat tolerant.

Common Name Scientific Name Regional Adaptation
Arizona Fescue Festuca arizonica N, SW, SC, SE
Big Bluestem Andropogon gerardii N, SW, SC, SE, HA
Blue Fescue Festuca glauca N, SW, SC, SE, HA
Blue Grama Bouteloua gracilis N, SW, SC, SE, HA
Blue Oat Grass Helictotrichon sempervirens N, SW, SC, SE, HA
Idaho Fescue Festuca idahoensis N, SW, SC, SE, HA
Indian Grass Sorghastrum nutans N, SW, SC, SE
Indian Rice Grass Oryzopsis hymenoides N, SW, SC, SE, HA
Little Bluestem Schizachyrium scoparium N, SW, SC, SE, HA
Prairie Dropseed Sporobolus heterolepsis N, SW, SC, SE, HA
Prairie June Grass Koeleria pyramidata N, SW, SC, SE, HA
Sand Love Grass Eragrostis trichodes N, SW, SC, SE
Side Oats Grama Bouteloua curtipendula N, SW, SC, SE, HA

Maiden grass

Maiden grass holds up well in winter. Photo courtesy of Judy Sedbrook

Naturalized Plantings

Many grasses will thrive under no-care situations in Idaho, even in the driest areas. They can be planted with native wildflowers and shrubs to create attractive, natural-looking landscapes. Some of the best grasses for naturalizing are spreading, rather than clumping in growth habit, giving them the ability to fill in bare areas.

Common Name Scientific Name Regional Adaptation
Arizona Fescue Festuca arizonica N, SW, SC, SE
Big Bluegrass Poa secunda var. canbyi N, SW, SC, SE, HA
Blue Fescue Festuca glauca N, SW, SC, SE, HA
Blue Grama Bouteloua gracilis N, SW, SC, SE, HA
Buffalo Grass Buchloe dactyloides N, SW, SC, SE
Crested Wheatgrass Agropyron cristatum N, SW, SC, SE, HA
Idaho Fescue Festuca idahoensis N, SW, SC, SE, HA
Prairie Dropseed Sporobolus heterolepsis N, SW, SC, SE, HA
Prairie June Grass Koeleria pyramidata N, SW, SC, SE, HA
Sandberg Bluegrass Poa secunda var. sandbergii N, SW, SC, SE, HA
Sheep Fescue Festuca ovina N, SW, SC, SE, HA
Snake River Wheatgrass Elymus wawawaiensis N, SW, SC, SE, HA

Winter grass

Tall grasses provide winter texture

Grasses for Winter Interest

Although consistently wet or moist soils are not common, especially in southern Idaho, such sites are often created artificially in the landscape. Below is a list of plants that thrive under such conditions.

Common Name Scientific Name Regional Adaptation
Blue Oat Grass Helictotrichon sempervirens N, SW, SC, SE, HA
Feather Reed Grass Calamagrostis x acutifolia N, SW, SC, SE, HA
Flame Grass Miscanthus ‘purpurescens’ N, SW, SC, SE, HA
Korean Feather Reed Grass Calamagrostis brachytricha N, SW, SC, SE
Maiden Grass Miscanthus sinensis N, SW, SC, SE
Northern Sea Oats Chasmanthium latifolium N, SW, SC
Switch Grass Panicum virgatum N, SW, SC, SE, HA

Penn Rub grass in container

Tender fountain grass makes a good container specimen. Photo courtesy of Judy Sedbrook

Tender Grasses Grown as Annuals

Some of the most attractive ornamental grasses are not hardy in Idaho. This includes many of the Pennisetum varieties that come in a remarkable array of foliage and flower spike colors. Many of these will still grow here if treated as annuals. Some of the tender grasses make very good container specimens. Here is a short list of tender grasses that can be grown as annuals.

Common Name Scientific Name Regional Adaptation
Feather Top Pennisetum villosum N, SW, SC, SE, HA
Lemon Grass Cymbopogon selloana N, SW, SC, SE, HA
Purple Millet Pennisetum glaucum N, SW, SC, SE, HA
Ruby Grass Melinus nerviglumis N, SW, SC, SE, HA
Tender Fountain Grass Pennisetum setaceum N, SW, SC, SE, HA
 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

Following proper guidelines for mowing, fertilization and irrigation will help keep thatch accumulation to a minimum. Mow at the proper mowing heights and follow the 1/3 rule to keep the grass from becoming stressed. Fertilization to avoid excessive growth also is important in preventing thatch buildup. Never apply more than 1 lb of nitrogen per 1000 ft² at any one time, especially in the spring when the grass is growing vigorously. Irrigate to encourage deep rooting will also keep thatch to a minimum. Remember to water ‘deep and infrequent’ for best results.

 August 16, 2012
Aug 162012

Your home lawn, like any other plant, needs water to grow and remain healthy and in Idaho that means irrigation will be needed. Lawns that become water stressed take on a gray to purplish-green color. Foot-prints on the grass also become more obvious when grass is stressed. The amount of water to apply at any one time and how often to water depends on several factors including soil type, time of year or weather conditions and the type of grass. Remember to irrigate early in the morning to take advantage of reduced wind, reduced evaporative losses and usually reduced demand on municipal water systems.

A thorough discussion of how to properly water a lawn may be found in the UI bulletin, Water Home Lawns: How Much and How Often.

 August 16, 2012
Aug 162012

Kentucky bluegrass and perennial ryegrass lawns may require up to 2 inches of water per week in the heat of the summer, but only about 1 inch in the cooler spring and fall. Turf-type tall fescue which uses the same or more water than Kentucky bluegrass may not need to be watered as frequently because it has deeper roots so it has a larger soil volume from which to absorb water. Buffalograss, at the other end of the scale, uses very little water and has a deep root system, so it can get by without water for several weeks.

 August 16, 2012
Aug 162012

During the spring in April to mid May when temperatures are still cool, most cool-season lawns in Idaho will use about one inch of water each week. From about late May to mid August, lawns will use about 2 inches of water per week or slightly more. Then, from mid August to late September they use just over one inch of water. During periods when significant amounts of precipitation is received, lawn sprinklers systems should be turned off. There is no need to irrigate when the soil is already filled to capacity.

Depending on the year and the onset of winter, grasses will still use close to an inch per week in October, and it is important to keep the soil moist, not overly wet, but moist going into winter. This will help prevent winter desiccation damage.

Lawns with significant shade and wind protection will not need as much water, but remember that the grass will be competing with tree roots for water and nutrients, so extra attention needs to be given to these landscapes.

 August 16, 2012
Aug 162012

Whether you have a sandy or clay soil will have a huge influence on the watering practices for your lawn. Sandy soils do not hold very much water and, therefore, lawns growing in sandy soils will need to be watered more frequently. The grass will still use the same amount of water per week, but if the soil cannot hold very much water, you will need to irrigate more frequently. Loamy and clay soils can hold more water than sandy ones and, therefore, lawns growing in clay type soils will not need to be irrigated quite as often.

In either case, apply enough water to penetrate the soil to the depth of the grass roots. Use a shovel or soil probe to determine rooting depth. For most clay type soils it may take 1 to 1¼ inches of water to fill the soil to a depth of 12 inches. For sandy soils, only ¼ – ¾ inch of water is all that may be necessary to fill the soil to a depth of 12 inches. Use a screwdriver to check moisture depth. The screwdriver should easily penetrate the soil to the desired depth you want the water.

In sloped areas, lawns with heavy thatch, or lawns growing in clay or compacted soils, water may need to be applied in small amounts separated by one-half hour increments to allow for adequate water infiltration and to prevent run-off.

 August 16, 2012
Aug 162012

Whether you are moving hoses and sprinklers or you have an automatic irrigation system, it is important to understand how much water your system is delivering in a given time period. One simple method to determine this is to set out several catch cans or rain gauges over the area to be irrigated. Run the system for 20 minutes, or a known amount of time, and measure the amount collected. Take an average of the can measurements, but also make note of those that are way off the average. This will tell you that you either have a nozzle problem or a rotating head that is stuck, etc. The average measurement can be converted to inches of water per hour and you can use this information to determine how long to run your system on a particular day. As mentioned above, a lawn’s water needs change with the season, so you should change your automatic sprinkler timers to deliver the correct amount of water depending on the time of year. In the spring, for example, you may need to water enough to replace 1 inch of water every 6 days, but in the summer when the grass is using more water, you may need to water every 3-4 days. Adjusting the timer several times during the season will reduce water waste and give the grass exactly what it needs.

While the system is running, it is a good idea to look for problems with sprinkler heads such as clogged nozzles or rotating heads stuck in one position. Clogged nozzles can be cleaned by unscrewing the nozzle or may involve unscrewing a set screw and pulling out the nozzle with needle nose pliers. On some sprinkler heads, the orifice may be replaced. However, if you don’t have a repacement, be careful not to damage the orifice. Sprinker heads that do not rotate may simply need to be cleaned, but usually need to be replaced as damage to the internal gears could also be a problem. Check your system each spring, taking the time to see each sprinkler operates to its full range since sometimes a head will get stuck at one end of the arc and not the other. Also, be sure the sprinkler heads are in a vertical position so the water is being distributed as designed.

The University of Idaho publication Watering Home Lawns and Landscapes provides a more detailed discussion on soil variables as well as an in depth discussion on proper use of automated irrigation systems.

Additionally, a website devoted to lawn and tree water management has been developed by the University of Idaho. In this website you can find water calculation tools to help you determine how much water to apply based on your irrigation system test: www.uidaho.edu/extension/lawn

 August 16, 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

Garden water demands and irrigation scheduling are the result of complex interactions between climate, weather, soil type, plant species, and irrigation practices. This means that there is no one recipe that is suitable for all gardens. Taking the time to learn about proper irrigation in your own situation will pay dividends. There are a few general principles that will help guide your decision on how best to irrigate your vegetable garden.

Scheduling Irrigation

Once the plants approach full size, typical water use for most vegetables will be ¼ inch (meaning that if you put a can under the sprinkler, the water inside would be ¼ inch deep at the end of the irrigation) per day. This means a summer garden will need around 2 inches of water per week. Because most soils will not hold this much water, plan to irrigate twice each week with the total being about two inches. In the spring when weather is cool and plants are small, they may use less than half this amount of water. In the fall, when plants start to mature, water use will also decline.

Soil Type

Plants use the same amount of water regardless of soil type. However, sandy soils hold less water and plants will use the water very quickly and then become stressed. So, if your soil is sandy, change your irrigation practices to water more frequently but put less water on during each irrigation event.

Irrigation System

Sprinkler irrigation is a simple method for making uniform applications of water to the vegetable garden. However, sprinklers wet the leaves and encourage disease development and they also splash dirt on leaves that may add some “grit” to your meals. If these are problems in your garden, consider using a bottom up irrigation method such as soaker hoses or a drip system.

 August 10, 2012
Aug 102012

When it comes time to plant a fruit tree, patience pays for itself many times over. Most of the problems we see with tree fruits come from two sources: failing to select appropriate crops for a site and failing to prepare the site before planting. We dealt with crop selection in Tree Fruits: Crops to Grow. Now let’s consider site preparation.

 August 10, 2012
Aug 102012

Native plants are receiving ever-increasing attention in the world of home and business landscaping. There are very good reasons for using native plants in our landscapes and gardens. These plants are adapted to local conditions. Consequently, they remain healthy and beautiful with less use of water, fertilizers, and pesticides. They can be used to create landscape themes that are in harmony with their surroundings. They also lessen the chance of importing invasive and destructive exotic species.

A scopulorum

But landscaping with native plants is not without problems. The main issues are identification of suitable native species for specific landscape uses and, maybe even more frustrating, finding source of native plants once a design is developed. The industries that market plants and designs for traditional landscapes have taken decades to meet customer demand and effectively supply myriad beautiful garden plants. It will likely take the native plant industry many years to become equally efficient. But, that is no reason for the native plant enthusiast to despair. There are beautiful plants for the landscape. There are also numerous small nurseries that can supply those plants. Lastly, there are designers that specialize in native plant landscape. You simply have to take the time to find the professionals that can supply what you need.

Sometimes, we think that using native plants in the landscape means adopting an unfamiliar palette of plants, or being limited to creating a front yard that looks like a sagebrush prairie (it should be said that elements of a desert ecosystem can make a very interesting and beautiful landscape). However, nothing could be further from the truth. The reality is that many native plants are already common in many of our most beautiful yards. Some of the plants we are all familiar with include white fir, blue spruce, Engelmann spruce, limber pine, red-twig dogwood, common juniper, Oregon grape, cinquefoil, currant, elderberry, ornamental fescues, many hyssops, columbine, some asters and daisies, blanketflower, coral bells, and many types of penstemons. Most of these plants can withstand a heavily watered yard, making them useful in a traditional landscape. Many other native plants can be used to create very attractive water-conserving landscapes.

University of Idaho researchers have begun a process of domesticating and evaluating native plants for use in Idaho landscapes. Although this research is in its infancy, it has resulted in considerable new information about native plants with horticultural value that are adapted to the dry conditions and high pH soils of southern Idaho. Dr. Stephen Love, leader of the native plant domestication project, has created a document that contains a list of native plants suitable for landscape use. The document also lists nurseries that supply these plants in quantities consistently sufficient for a home landscape project and sometimes sufficient for much larger projects.

The document, entitled Dr. Love’s Favorite Native Plants and Where to Buy Them can be viewed and downloaded by clicking on the link attached to the title. Questions concerning the document can be directed to Dr. Stephen Love.

 August 10, 2012
Aug 092012

On the surface, watering home landscape or garden plants appears to be simple and straightforward. However, it is complicated by a number of factors including climate, available water source, weather, topography, soil type and the irrigation system available. As a result, irrigation is poorly accomplished by most homeowners. In fact, many homeowners fall prey to over-watering, wasting money and natural resources. Irrigation has a greater impact on plant health in Idaho landscapes than any other input, so doing it properly is critical.

Watering cands and sunflowersMany landscape trees are lost each year because the root zone was not adequately watered in the late fall, and young trees are often damaged or killed by over-watering. Water-stressed plants are subject to increased insect and disease problems and decreased winter hardiness. Excess watering leaches out nutrients and pesticides that can pollute ground water. As you can see, it is very important to understand how to apply the proper amount of water. Important decisions associated with proper irrigation include choice of equipment, determination of irrigation frequency, and knowing how much to apply.

There are several types of irrigation systems, each with advantages and drawbacks. Most homeowners use some type of sprinkler application, some manually controlled and others automated, while some flood irrigate. Drip irrigation is becoming popular as it can conserve large amounts of water, as well as aid in weed control. Whatever the method, it is important to know the application rate of the system and the application is uniform. To properly irrigate, the root zone should be completely filled with water, and then allowed to partially dry between irrigations so to ensure adequate oxygen for the roots. The root zone for lawns is about 10 to 12 inches, vegetable gardens 18 inches, shrub beds up to 2 feet, and trees approximately 3 feet.

Three important pieces of information are needed to properly irrigate: 1) the application rate of the system, 2) the amount of water plants are using, and 3) the amount of water required to fill the root zone. The University of Idaho has published a detailed and valuable document on using this information to determine best irrigation practices, Watering Home Lawns and Landscapes.

Soil type (texture) has a large impact on irrigation practices. Sandy soils may hold enough water for only a single day of plant growth. Fine-textured such as silt or clay soils may hold enough for 5 or 6 days. Consequently, it is important to adjust watering practices based on soil texture. In principle, sandy soils will need a very light application of water on a very frequent basis. Heavier soils will need water less often, but will need a larger amount at each irrigation event. Soil texture does not change the amount of water plants need or use, but it does change the schedule (frequency) for supplying the water.

One of the problems of irrigating landscapes and gardens is that multiple plant species, each with their own water requirements and rooting depths, are grouped together. For most plants in a mixed garden or landscape, it is adequate to water to a depth of about 1 foot. However, if trees or shrubs are part of the landscape, for every third or fourth irrigation, the sprinkler system should operate long enough to fill the root zone with water to a depth of 2 to 3 feet. After filling the root zone to a 2- to 3-foot depth, the interval to the next irrigation should not change. On the next irrigation, run the irrigation system just long enough to fill the root zone to 12 inches.

In areas with limited water supplies, there are ways to conserve. One is to select plants that need limited amounts of water. Many of our Idaho native plants are adapted to dry summer conditions. Another way to conserve moisture is to use mulch in flower beds and around trees to limit evaporation from the soil surface.

Find additional help with calculating water needs for lawns and trees at University of Idaho Extension. For an in depth discussion on calculating amount of water to apply to a lawn, see University of Idaho bulletin Watering Home Lawns: How Much and How Often.

For a general discussion of home landscape water management, see the Montana State University publication Yard and Garden Water Management.

The University of Georgia supplies an outstanding discussion of irrigation systems in the bulletin, Irrigation for Lawns and Gardens. For a listing of water conserving plants adapted to Idaho, see Washington State University bulletin Hardy Plants for Waterwise Landscapes.

 August 9, 2012
Aug 062012

Ensure that the soil around the tree does not become dry, but avoid overwatering. Your goal should be to keep the soil moist, but not waterlogged. Some gardeners like to build a shallow saucer around newly-planted trees by creating a raised lip of soil about 12 to 24 inches in diameter. This practice can be helpful on soils that drain well until the tree becomes established. On heavier-textured soils, building such saucers can cause problems with the trees. As a general rule, if you build a tree saucer and fill it with water, the water should have drained completely away within an hour or so. If not, remove the saucer. Check newly-planted trees twice weekly to ensure proper irrigation.

 August 6, 2012