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Aug 132012

Plants are pruned for a variety of reason. Prune plants to maintain health and desired appearance by pruning out dead, diseased and unwanted branches. Old flowers and fruit should also be removed as they may become unsightly. Pruning faded flowers (dead heading) enables the plants to put more energy into growth versus making seeds. By pruning plants regularly you can control size and appearance without having to prune extensively. Late fall is a good time to evaluate deciduous plants for pruning after the leaves have fallen.

 August 13, 2012
Aug 132012

Selecting the proper time to prune is important. Heavy pruning at the wrong time of year can stimulate unwanted growth or prevent flowering or fruiting. Before pruning, consider time of year, type of plant and flowering periods of certain plants. See the table below.

Time of Year to Prune Various Types of Plants.
Type of plant Fall Winter Spring Summer Comments
Early Late Early Late Early Late Early Late
Deciduous shrubs for shrubs
that flower before
June 1
Deciduous shrubs for shrubs
that flower after
May 30
Conifers –
Shrubs and
All conifers
except for pines
(see below)
For shrubs grown
for flowers
Broad leaf
For shrubs grown for foliage (hedge)

When to Prune New Growth on Pines

Pines have buds only at the tip of the branches. If a branch is pruned after a growth flush and the terminal bud is removed, regrowth is impossible. Pine branches should be pruned or pinched in early summer when the new branch (candle) has begun to elongate but before the needle bundles open. This pruning causes the growth to be more compact but still allows buds to form for the following year.

 August 13, 2012
Aug 132012

1. Heading Cut – Cutting plant stems back to a bud, twig or stub. Potential problems – a stub is often left and may become infested with insects or diseases, vigorous growth may be stimulated, and the new growth may be weakly attached and could split or crack under pressure. This may also negatively affect the desirable, graceful arching habit of some shrubs.

Heading cut

2. Thinning Cut – The removal of a branch at its point of origin or cutting back a branch to a lateral branch about 1/3 the diameter of the branch being removed. Advantages – No stub is left, the plant retains its natural shape, and vigorous new shoot growth is avoided. Caution: removing more than about 30% of the foliage can stimulate new growth even if thinning cuts are used.

Thinning cut

Using thinning cuts on selected branches to improve light and air penetration to interior foliage

 August 13, 2012
Aug 132012

The size of the branch determines the location of the pruning cut. A small twig or branch can be pruned back to a bud or lateral branch. On a small branch make the cut one-quarter inch above the bud, and slant the cut away from the bud (see diagram).

Length of pruned stub

1. Natural target pruning is the technique used when cutting beyond the bark ridge and branch collar (collectively called the branch shoulder). see diagram below. This cut provides a physical barrier to disease and injury within the intact branch shoulder. This compartmentalization of the wound stops injury from spreading into the main trunk of the plant where it could spread throughout the plant and be damaging to the plant as a whole. The wound size is also smaller allowing callus to grow quickly over the wound and limits potential exposure to insect and disease infestation.

Natural target pruning

2. Large branches or limbs (those to heavy to hold while cutting) are removed by a series of three cuts. The first cut is made on the underside of the limb about 12 inches from the branch crotch and should go about one -quarter of the way through the limb. The second cut is made on the top side of the branch about 2 inches farther out on the limb from the undercut. Cut down until the branch cracks off. As you are completing the second cut, careful to watch for the branch suddenly dropping or moving quickly as the branch weight accelerates limb removal. The third cut is made on the top side of the stump left over, just outside of the bark ridge and branch collar. See the diagram (on next page) to determine where the final pruning cut should be made. Be sure to support the branch stump when making the final cut to avoid tearing the tissue when completing the cut.

Three cut method diagram for pruning large branches:

Three-cut method for pruning

 August 13, 2012
Aug 132012

Proper tools should be used to make a clean pruning cut and to minimize damaging plant tissue. If the plant tissue is crushed or torn it can leave the plant susceptible to disease and insect problems. In addition, more time will be needed by the plant to have tissues grow over the wound. Pruning tools should be the correct size for the job and be made of tempered steel that can hold a sharp edge. Making a pruning cut should be relatively easy when the correct size of tool is used. Hand pruners should be used to cut branches that are less than one-half inch in diameter. Lopping shears should be used for branches between one-half and 1 inch thick. A bow saw or pruning saw should be used to cut branches larger than 1 inch thick. Be sure to make a clean cut with the proper tool.

Sanitizing pruning tools

Pruning tools should be disinfected after each cut, under ideal circumstances, to avoid spreading diseases from plant to plant. At the very minimum disinfect pruning tools after finishing one plant but before beginning to prune the next plant. To sanitize tools, dip the cutting edge in a disinfectant solution such as denatured alcohol, methanol or diluted household bleach (1 part bleach plus 9 parts of water). An alternative is to spray the cutting blade with a disinfectant solution. When using bleach, make sure to apply a thin layer of oil to the blade before storing to avoid rusting of the tool.

Pruning paints and asphalt emulsions are not recommended for use on pruning cuts as they may actually seal in disease-causing organisms or promote rot.

 August 13, 2012
Aug 132012

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

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

 August 13, 2012
Aug 102012

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


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

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

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

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

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

Selecting a Site

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

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

Pests and Diseases

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

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

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


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

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

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


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

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

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

Weed Control

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

 August 10, 2012
Aug 102012

Pest and Disease Management
Fruit Thinning

Healthy and productive fruit trees require regular care throughout the year. A few of the more important tasks are listed here. Click here for links to more complete guidance on fruit tree care.

In early spring before the new leaves appear, examine the trees carefully for signs of damage from winter cold, snow and ice, diseases, girdling or other damage from animals, and signs of pests or pest damage.

Prune your fruit trees. Normally, we prune fruit trees in late winter or early spring before the buds begin swelling. First remove any diseased or damaged wood. Damaged and diseased wood can be pruned out any time of the year. If the branch is or may be diseased, rinse your pruning shears after every cut in a solution of 20% household bleach in water or 70% ethyl or isopropyl alcohol. Do not compost diseased or pest infected branches.

Remove all sprouts arising from the roots and trunk below the graft union. Next, concentrate on building a strong structure that will support the branches and crop. Remove enough wood to maintain an open canopy that allows light to penetrate to the trunk and air to circulate freely through the tree. Most water sprouts come off at this time. Water sprouts are vigorous, vertical shoots that can easily develop into multiple leaders and create a crowded, hard to manage tree. With some crops, pruning can help manage the tree height by removing branches above a desired height. Height management through pruning works well for peaches, nectarines, and apricots. For apples and pears on dwarfing rootstocks, pruning is also valuable for controlling height. Controlling cherry and plum tree height with pruning can be difficult.

 August 10, 2012
Aug 092012

When we consider pruning, we naturally think of early spring. This is appropriate for the most part, because removal of branches on a plant is best done after winter cold has abated and before the plants leaf out. This helps prevents excessive weeping (sap flow from the wound) and allows time for wounds to heal during the summer months. However, there are practical reasons for completing some minor pruning during the summer.

Pruning may be needed to remove damaged or diseased branches that were not apparent during the spring. There may also be a need to remove branches with winter injury, something that does not become visible until warm weather arrives. For some shrubs, pruning may also be needed to remove spent flowers to encourage the growth of new blossoms. Fruit trees can be pruned to remove some fruit in years that fruit set is excessively high. This will result in larger fruit and help prevent alternate bearing, the tendency for fruit trees to grow fruit only in every other year.

Summer pruning

One of the main reasons to prune shrubs and trees in the summer is to control size. When pruning is done only in the spring, trees and shrubs tend to sucker where old branches are removed. These new branches grow rapidly and if left in place result in overall increased size. Removal of these new branches during the summer helps a tree or shrub to remain small in stature and more compact in shape. It will also decrease the amount of pruning needed during the next spring.

Even conifer trees can by pruned to control size. This is done by clipping off most of the “candle”, the new sprout of soft growth that emerges in the spring. This will help keep a potentially large tree small, while at the same time helping to thicken the new growth. When pruning evergreens, it is important not to remove all of the new growth (except occasionally). This will leave only older wood that will eventually lose its needles and become unattractive.

Pruning for size control with shrubs may take the form of shearing, something we do to manage the size and shape of hedges and specimen plants in the yard. Shearing not only removes lanky, tall growth, but causes the plant to branch out and become thicker.

So, don’t be afraid to break out the pruning tools in July. Selective summer pruning will improve the look of your yard.

 August 9, 2012