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Aug 172012
 
Revennae grass

Revennae grass serves the role of pampas grass in cold climates. Photo courtesy of Judy Sedbrook

As with any perennial, proper site selection is critical for success with ornamental grasses. Soil preparation in a perennial bed is completed only one time, just prior to planting and must be done properly. First, kill and remove any persistent weeds, especially grasses. Such weeds are difficult to manage once the beds are planted. This may take several months and multiple applications of a systemic herbicide. Except in native naturalized plantings, amend the soil by adding 2-3 inches of well-aged compost or manure. This is especially important in the arid, calcareous soils of southern Idaho. Add the equivalent of 3 lb/1000 sq. ft. of nitrogen in the form of a complete fertilizer, such as 5-10-5.

After amendments are added, the soil should be tilled to a depth of at least 8 inches, leveled, and smoothed (but not packed). Just prior too or after planting, it is a good idea to add two or three inches of mulch (wood chips, bark, etc.) to the soil surface. It may also pay dividends to place some type of edging or border around the bed to slow encroachment of grass or other weeds.

 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.

Mulching

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

Irrigation

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.

Fertilization

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.

shears

Grasses can be cut back in fall or winter

Manicuring

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.

snail

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.

Mulching

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.

Hose

Bulbs require deep watering

Irrigation

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.

Fertilization

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.

Staking

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.

Pruners

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.

slug

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 172012
 
Perennial weeds must be controlled before planting

Perennial weeds must be controlled before planting

Proper site selection is critical for success with perennials. Because the plants will reside in the same place for many years, they must be adapted to conditions where planted. If not, they may never reach their full potential for beauty in the landscape.

Major soil preparation in a perennial bed is completed only one time, just prior to planting. Consequently, to avoid future difficulties it must be done properly to ensure a healthy environment. First, kill and remove any persistent weeds and grass. Such weeds are difficult to manage once the beds are planted. This may take several months and multiple applications of a systemic herbicide. Next, make sure the site has good quality topsoil. This may require addition of topsoil, particularly in new home sites. Amend the soil by adding 2-3 inches of well-aged compost or manure. This is especially important in the arid, calcareous soils of southern Idaho. Add a complete fertilizer such as 5-10-5 at the equivalent of 3 lb/1000 sq. ft. of nitrogen. The fertilizer choice should be high in phosphorus and should preferably include sulfur in southern Idaho.

After amendments are added, the soil should be tilled to a depth of at least 8 inches, leveled, and smoothed (but not packed). Just prior to, or immediately after, planting it is a good idea to add two or three inches of mulch (wood chips, bark, etc.) to the soil surface. It may also pay dividends to place some type of edging or border material around the bed to slow encroachment of grasses or other weeds.

 August 17, 2012
Aug 172012
 

Once established, most perennial plants are relatively carefree. In general, they require less in the way of fertilizer and water inputs than do annuals. However, as is true of all plants, some tender loving care is needed to keep them healthy and attractive.

wood chips for mulching

Wood chips as a mulch layer

Mulching

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

Irrigation

Perennial plants should be irrigated less often and to a greater depth than nearby lawn areas. Many perennial plants have effective rooting depths of up to three feet. 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. A few perennials are adapted to very moist or even saturated soil conditions. These must be watered more often.

Fertilization

Most perennial plants 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 of the plants. If the previous year, plants were slow growing, small, or yellow in color, add fertilizer at the higher end of the recommendation. If they were growing well and looking nice, add at the low end of the recommendation. If they were vigorous, floppy, and too large, do not add any fertilizer.

seed head

Removing old seed heads will aid flowering

Manicuring

Although relatively carefree, some perennials need attention to remain attractive throughout the summer. Plants that look thin and leggy can be forced to produce more lateral growth by shearing or pinching off the growing point of each stem. Plants that have many stems may produce bigger stems and larger flowers if some of the stems are pruned out. Removing lateral flower buds, leaving only the top-most bud, will also make flowers larger. Plants that fall down or become floppy may need to be staked or interplanted with stiffer, more upright types of plants. Deadheading will prolong flowering of many perennials and make the plants more attractive.

Weed Control

There are no options to completely replace hand weeding in annuals. 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.

Perennials may require winter protection

Perennials may require winter protection

Winter Protection

In the fall, perennials (except those that provide some winter interest or seedheads for sustaining birds and other wildlife) should be cut back to a height of 3-4 inches. This will create a more attractive winter landscape and allow the crowns to be covered with a layer of mulch. 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 and rot in wet spring climates.

Disease and Insect Control

It is beyond the scope of this site to provide specific pest management information for the large number of commercially available perennial 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 for these common pests in our sections on insects and disease problems. 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.

Aphids with a predatory lady bug larvae ©2004 Cornell Plant Pathology Herbarium

Aphids with a predatory lady bug larvae ©2004 Cornell Plant Pathology Herbarium

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.

Caterpillars can be destructive

Caterpillars can be destructive

Caterpillars: Are the larvae of numerous species of moths and butterflies. These voracious legged worms come in many sizes and colors. Plant symptoms include chewed or completely missing leaves. Some types of caterpillars will roll or fold the leaves and hide inside. Often, frass or droppings are present on and around the plants.

A light infestation can be easily controlled by picking them from the plant a crushing them. Common registered insecticides will effectively kill caterpillars.

Leafminers: Are small insect larvae that burrow under the leaf surface while feeding. Symptoms are easily recognized and exhibit themselves as zig-zag or wandering lines on the upper leaf surface that are lighter in color that the rest of the leaf surface. These are tunnels in the leaves caused by leafminer feeding.

A light infestation of leafminers can be controlled by removing and destroying damaged leaves. A heavy infestation will require the use of a registered systemic type insecticide.

Mealybugs: Are sucking insects that infest stems of many plants. Mealybugs are easily recognized by the presence of a cotton-like white substance they deposit for protection.

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.

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 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.

Whiteflies: In Idaho are more commonly a problem in greenhouses than they are outdoors. They are small insects with distinct bright white wings that reside and feed on the underside of leaves. Symptoms include the presence of honeydew on leaf surfaces, often accompanied by a lack sooty mold. When disturbed, clouds of the white, rapidly flying insects will rise above the foliage, then quickly resettle.

Trap the flies with yellow sticky boards or use a registered insecticide.

Disease Problems

Damping Off: Caused by fungal pathogens that infect seedlings at soil level, girdling the stems and causing death. Infected seedling will develop tan-colored, soft tissue at the base of the stem. The plants fall over and usually die. Once established and actively growing, plants seldom are affected by damping off.

Control measures include maintaining optimum soil moisture and planting into well-drained soils that are not overly wet. In extreme cases, a soil drench of a registered fungicide can be applied to the soil surface. However, by the time damage is observed it may be too late for control using fungicides.

Leaf Spots: Are caused by numerous fungal (occasionally bacterial) pathogens that penetrate and kill leaf tissue. Symptoms usually start and are worse on older leaves. These diseases are usually worse following periods of wet weather and high humidity.

Removal of all dead plant material at the end of the growing season helps prevent many leaf spot diseases the following year. In-season control usually requires use of a registered fungicide.

Powdery mildew on a perennial plant © 2004 Cornell Plant Pathology Herbarium

Powdery mildew on a perennial plant © 2004 Cornell Plant Pathology Herbarium

Powdery Mildew: Is caused by fungal pathogens. The classic symptom is a whitish, powdery growth present on leaf surfaces. Heavy infections cause distortions on new growth. Infections are often worse during summers that follow damp spring weather. Plants grown in shade are more prone to infection with powdery mildew

Prevention involved growing plants in a sunny location and making sure there is plenty of space and air movement around plants. Control usually requires the use of a registered fungicide.

Root and Stem Rots: Are caused by fungi (occasionally bacteria) that live in the soil. Infected plants initially develop mild wilting symptoms that become progressively worse and may eventually cause death.

Soil pathogens are difficult to control. They can best be prevented by planting resistant varieties, avoiding overly wet soil conditions, and destroying infected plants.

White Mold: Is caused by a fungus that overwinters in the soil. It infects plant stems that touch moist soil surfaces. Symptoms include a slimy, white mold that girdles and collapses the infected tissue. Leaves above the girdled stem wilt and die. In advanced stages, small gray structures that look like mouse droppings form inside a hollowed stem.

Prevention is the best strategy and involves staking stems off the ground, spacing plants to allow air movement around foliage, and irrigating infrequently to allow intermittent drying of the soil surface.

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 perennials because their long life span and lack of seed propagation create many opportunities for chronic infection.

There are not 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.

Diagnosis information and specific control measures for diseases in the landscape is available from the University of Kentucky.

The University of Illinois Extension has published a bulletin on control of common insect pests in flower gardens.

 August 17, 2012
Aug 162012
 

Once established, many annual plants are relatively carefree. However, as is true of all plants, some tender loving care is needed to keep them healthy and attractive.

mulch

Mulch provides many benefits

Mulching

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

Irrigation

Annual flowers use about the same amount of water as does lawn, equal to about ¼ in. per day during July and August. In most Idaho soils, this means approximately 1 in. of water should be applied every 4 to 5 days. 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. The simplest method of judging water need is to wait between irrigations for the top 1-2 in. of soil to dry.

Fertilization

In most loam soils, preplant fertilization may be adequate to provide basic nutrient needs for annual plants. However, under conditions of sandy soils or long growing season, there may be benefit in adding a small amount (equivalent of 2-3 lb nitrogen per 1000 sq. ft.) of a fertilizer that is high in nitrogen. Sprinkle the fertilizer on the soil surface and water it in. Make the application in late June or about the time the flowers reach peak bloom.

Manicuring

Some annuals need a little attention to appearance to remain attractive. Plants that look thin and leggy can be forced to produce more lateral growth by shearing or pinching off the growing point of each stem. Plants that fall down or become floppy may need to be staked or interplanted with stiffer, more upright types of plants. Many annuals either do not shed dead flowers or produce seed heads, thus reducing production of additional flowers and making the plants less attractive as the summer progresses. This can be solved by occasionally removing the dead flowers, a practice called “deadheading”.

seed head

Removing old seed heads encourages flowering

Weed Control

There are no control options that completely replace hand weeding in annuals. Mulching with organic matter or weed barriers will help by blocking germination and growth of weed seed. Some partially effective herbicides are available to help with weed control in annuals. All of these must be applied after the flowers emerge or are transplanted, but before the weeds emerge. See your county agent or local nurseryman for information on products available.

Disease and Insect Control

With over a hundred species of annual flowers commonly available, it is beyond the scope of this site to provide specific pest management information for each one. However, there are many pests that are common and infest many types of plants. We have compiled information on the most common of these in our pages on insect and disease problems.

For more detail on control of insects and diseases, as well as information of other pests not covered in the sections above, see the Insect and Disease Pests section of this site.

 August 16, 2012
Aug 162012
 

Most weed problems in lawns are associated with a weak, thin turf. A thin turf is easily pushed aside by aggressive weeds which can become worse over time. Make sure to follow good fertilization, irrigation and mowing guidelines to build a thick, vigorously growing lawn. Heavy weed populations are usually an indication of some other inherent problem with the lawn.

Some perennial weeds, like white clover, can still become problems even in well managed lawns. Many herbicides are available to effectively control weeds in lawns, but their success largely depends on proper application, and perhaps more importantly, on correct timing. Knowing what weeds you have will help you determine the best time of the year to control them.

Realize that it is impossible to eradicate all weeds from a lawn even with herbicide use. Learn to tolerate some weeds in your lawn and avoid indiscriminate use of herbicides which can injure trees, surrounding landscape plants and even the lawn itself.

Photographs of many weeds can be found at WSSA’s Photo Gallery.

Perennial Broadleaf Weeds

Some common perennial broadleaf weeds in home lawns include dandelion, field bindweed (also called morningglory), white clover, curly dock, ground ivy, Canada thistle, broadleaf plantain, buckhorn plantain and yarrow. Make sure to properly identify the weeds before choosing herbicides for control. University of Idaho extension educators, master gardeners and nursery personnel can help you with correct identification.

Broadleaf weeds can be controlled with postemergence herbicides (a chemical that is applied to weeds after the weeds have emerged from the soil) which kill weeds that are actively growing. Postemergence herbicides do not prevent weeds from germinating.

The best time of the year to control perennial weeds is in late summer or early fall when the weeds are preparing for winter. In preparation for winter, perennial weeds move energy reserves from the leaves to underground stems and roots, so a herbicide application at this time will ensure movement of the herbicide to these plant parts, thus resulting in a more effective kill because the roots are being affected. Spring applications to perennial weeds can slow their growth and may kill them, but it is more difficult. Regardless of when applications are made, make sure the weeds are actively growing at time of application. Avoid mowing for 1 to 2 days before and after the application to ensure maximum uptake of the herbicide by the weeds.

There are many broadleaf weed control products available for home use. These products will contain one or a combination of the following chemicals: 2,4-D, 2,4-DP, MCPP, MCPA and dicamba. They are safe to use on cool-season lawn grasses. Liquid and granular formulations of these chemicals are available. It is very important to properly calibrate sprayers or granular spreaders to ensure accurate, uniform application and avoid spraying adjacent flower beds or susceptible plants. Be sure to read and follow all label directions.

Perennial Grassy Weeds

Perennial grassy weeds are the most difficult weeds to control in a home lawn. Some common perennial grassy weeds include quackgrass, roughstalk bluegrass, smooth bromegrass, annual bluegrass (there exist some perennial biotypes) and even other cool-season grasses such as tall fescue and creeping bentgrass. There are essentially no herbicides available for the selective control of these weeds in a lawn. Removal of these problem weedy grasses prior to establishing a lawn and the use of high quality seed or sod is essential to preventing these weeds from becoming a problem. Many home lawns are established with poor quality seed that has high amounts of weeds such as annual bluegrass and roughstalk bluegrass. What is contained in a seed lot you are considering to purchase is readily available on the seed label, but most homeowners are unaware of its importance. If small patches of perennial grasses are found in a lawn, physical removal with a shovel or spraying with a non-selective herbicide such as glyphosate is the only option followed by re-seeding or sodding the bare areas.

Annual Grassy Weeds

Weeds like crabgrass and foxtail are warm-season grasses that germinate from seed in the spring and infest lawns during the hot days of summer. They tend to invade lawns along sidewalks and driveways where temperatures are hottest and lawns are thin. Thick, vigorously growing lawns will out-compete most annual grassy weeds.

Annual grassy weeds are best controlled with pre-emergence herbicides (a chemical that is applied before the seeds have germinated) which kill germinating weeds. These herbicides must be applied well before the weeds germinate since they will not kill weeds once they have emerged. Additionally, some of these pre-emergence herbicides are impregnated on fertilizer granules and applied as a weed and feed. Crabgrass will germinate when soil temperatures reach 55 to 60º F. This occurs around mid-March to early April for the Treasure Valley, Magic Valley and northern Idaho and late March to mid-April for central and eastern Idaho.

There are some herbicides that will kill young annual grasssy weeds, but they usually only work well on very young plants so application timing is critical.

Do not overseed into areas that have recently been treated with pre-emergence herbicides because the chemical will kill emerging lawn grasses as well. Check the label of the herbicide to see how long you need to wait before planting into an area treated with a pre-emergence herbicide.

 August 16, 2012
Aug 102012
 

Weeds steal water and nutrients, compete for available light, and reduce the yield and quality of the vegetables. Although weeds will always be present, there are some methods for control that will make them easier to live with.

Cultivation

Hand pulling and digging weeds is probably the best choice for small gardens and raised beds. Hoeing is preferred in larger spaces. Hoeing can damage root systems of larger plants, so push the blade of the hoe only deep enough into the soil to sever weed roots and stay several inches away from the base of the vegetable plants. Manual powered rotary cultivators can supplement the use of a hoe and do a good job on long rows and pathways if the soil is not too wet or dry and if the weeds are not too big.

Cultivation is best done when the soil is somewhat moist, but not wet. The best time to cultivate is two or three days after rain or irrigation. Working wet soil will damage the structure, especially of fine-textured soils, making them compacted and cloddy. On the other hand, when the soil is too dry, weeds are difficult to pull and hoeing is a chore (beyond its usual tedious nature).

MulchingMulching

A thick layer of organic mulch will prevent most annual weed seeds from germinating and those that do are usually easily pulled. Organic mulches can include straw, grass clippings (make sure they are free of herbicides), bark (small enough to be tilled under at the end of the season), wood chips, or sawdust.

Mulching with black plastic film can also be very effective in reducing weed growth. Using black plastic mulch on the rows and an organic mulch between the rows will nearly eliminate annual weed problems..

Close Spacing

Established vegetable plants will shade the soil and prevent the growth of many weed seedlings. The plants are spaced so that the foliage of adjacent plants touches and forms a closed canopy at a mature growth stage.

To learn more about controlling weeds, see the following publications:

From North Carolina State University: Weed Control in Vegetable Gardens
From Cornell University (very detailed): Weed Control for the Home Vegetables Garden

 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.

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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

Gooseberries

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.

Varieties

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.

Pruning

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 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