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Aug 132012
University of Idaho


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

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

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


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

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

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

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

Management of White Pine Weevil in Spruce


Controlling Iron Deficiency in Plants in Idaho

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

Nutrient Disorders in Tree Fruits


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

University of Illinois

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

Pine Wilt
Pine Diseases Chart
Phomopsis Blight of Juniper

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

Ohio State University

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

University of Vermont
Pest Management
University of Massachusetts

Helping Trees Recover from Stress

University of Minnesota

Garden: Trees & Shrubs – Insects/Diseases

Ohio State University


 August 13, 2012
Aug 102012

Strawberries are one of, if not the most, adaptable fruit crops in the world. These tremendously popular berries are grown from the tropics to near the Arctic Circle. Besides their appeal as fresh fruits, strawberries can be easily processed into jams, jellies, pastries, syrups, fruit leathers, and many other tasty treats.

Download our free how-to guide!
Growing Strawberries in the Inland Northwest and Intermountain West

All Strawberries

Optimum pH: 5.5 – 7.0
Productive life: 2 to 3 years

June-Bearing Strawberries

Expected yield: 0.5 to 1 pound per foot of row during the second and third year
Fruit years: second and third

  • Matted row: 12 to 18 inches apart in rows 36 to 48 inches apart
  • Ribbon row: 4 to 9 inches apart in row 36 inches apart
Everbearing Strawberries

Expected yield: 0.25 to .05 per pound of row during the second and third year
Fruiting years: second and third

Dayneutral Strawberries

Expected yield:

  • Year 1: 0.25 to .75 pound per foot of row
  • Years 2 and 3: 0.5 to 1.5 pound per foot row

Fruit years: first, second and third

  • Matted row: 12 to 18 inches apart in rows 36 to 48 inches apart
  • Ribbon row: 4 to 9 inches apart in row 36 inches apart

StrawberriesStrawberry varieties fall into three categories: June-bearing, everbearing, and day-neutral. June-bearing strawberries respond to the short days of autumn by setting flower buds. In the late spring or early summer of the following year, a June-bearer produces a single, heavy crop of strawberries. Remove all flower blossoms that form during the planting year to encourage strong, healthy plants. Begin cropping your June-bearers the year after planting. Replace beds more than three years old.

Everbearing strawberries also set flower buds in fall, but do so again during the long days of summer. In this way, these varieties bear two moderate crops each year: one in the late spring or early summer and another in the late summer and early fall. Particularly during cool growing seasons, everbearers produce a trickle of fruit throughout the summer. As with June-bearers, remove all flower blossoms that form during the planting year. Replace beds more than three years old.

Dayneutral strawberries set flower buds throughout the spring, summer, and fall. Theoretically, they should bear a continuous crop of fruit from late spring until fall frosts. In actuality, they behave more like everbearers under Idaho conditions, with moderate to heavy crops in the spring and fall, and a smaller stream of berries in between. As is true with the everbearers, cool weather during the summer encourages flower formation and fruiting. Day neutral varieties yield more than everbearers. Remove all blossoms that develop between spring planting and early August. You can begin cropping dayneutral varieties during fall of the planting year. Because they come into production the year of planting, rather than in the second year, yields over the life of the planting are greater than for June-bearers.

Although they are highly adaptable, good site selection, site preparation, and variety selection are critical if you are to be successful with strawberries. The best sites have deep, moist, well drained soils. Sandy loams are best, but most loams are satisfactory if drainage is provided. Strawberries do not tolerate either drought or wet soils well. Commercially, most strawberries are grown on raised beds about 12 inches high and 18 inches wide. This practice is also excellent for home gardeners. For details on planting designs and crop care, download a copy of Growing Strawberries in the Inland Northwest and Intermountain West.

Selecting the right variety for your site is important. Cold hardiness, for example, ranges from slightly below freezing to ­50°F. Resistance to common strawberry diseases also varies greatly among varieties.

 August 10, 2012
Aug 102012

Raspberries are among the most popular and easy to grow small fruits for Idaho gardeners. Depending on the variety, the plants adapt well to a range of soil conditions and can be quite cold hardy. These popular fruits can be eaten fresh or made into jams, jellies, syrups, compotes, pastries, juices, and many other foods. Besides their excellent flavor, raspberries provide vitamin A, vitamin C, and dietary minerals. You can choose varieties that produce a single heavy crop in late spring to mid summer or two smaller crops in late spring to mid summer and again in late summer or early fall.

Download our free how-to guide!
Growing Raspberries and Blackberries in the Inland Northwest and Intermountain West

All Raspberries

Age to maturity: 3 to 4 years
Productive life: 8 -12 years or more
Optimum pH: 6.2 to 6.8

Black Raspberries

Expected yield: 2.5 to 3 pounds per hill
Hardiness: -5 to -10° F
Plant spacing: 3 feet apart in rows 8 to 10 feet apart

Purple Raspberries

Expected yield: 3 to 4 pounds per hill
Hardiness: -15 to – 20° F
Plant spacing: 3 feet apart in rows 8 to 10 feet apart

Red & Yellow Raspberries

Expected yield: 2 to 3 pounds per hill
Hardiness: -20 to – 25° F
Plant spacing:

  • Summer-bearing: 2 to3 feet apart in rows 8 to 10 feet apart
  • Fall-bearing: 2 feet apart in rows 10 feet apart

Raspberries come in four colors: red, yellow, back, and purple. Red and yellow raspberries are the same species, differing only in color, and are the most cold hardy of the brambles. A few varieties tolerate winter temperatures of -20 to -25 °F and many are hardy to -20 °F. Black raspberries belong to a different species and can be injured by temperatures between -5 and -10 °F. Purple raspberries are crosses between red and black raspberries. They are very vigorous, highly productive, and fall somewhere between red and black raspberries in cold hardiness. In Idaho trials, purple raspberries survived winter temperatures of -20 °F with no injury.

Raspberries produce either one or two crops of fruit each year. Summer-bearing raspberries produce a single crop of fruit beginning in late spring to mid summer. Fall-bearing (also known as everbearing or primocane-bearing) raspberries produce a crop in late spring to early summer and another crop in late summer or early fall. Red and yellow raspberries may be either summer- or fall-bearing. All black and purple raspberries are summer-bearing, but some varieties may develop terminal fruits on the first-year canes (primocanes) during exceptionally long, warm growing seasons. By growing several varieties, you can enjoy fresh berries from late spring through late fall.

Raspberries grow best on deep, well drained soils. Although raspberries tolerate a relatively wide range of soil pH values, wet soils can create serious problems with root rot diseases. Red and yellow raspberries are especially susceptible to poor drainage and root rot. Some black and purple varieties are less susceptible. If you have a heavy-textured or otherwise poorly drained soil, grow your raspberries on beds at least 12 inches high and three to four feet wide. For small beds where heavy soils are present, consider mixing sand into the soil in the beds. Do not apply organic mulches to heavy or poorly-drained soils; doing so increases problems associated with cold, wet soils.

 August 10, 2012
Aug 102012

Grapes are an immensely popular fruit crop with gardeners worldwide and Idaho gardeners are no exception. Idaho has commercial table and wine grape industries, located mostly in southwestern Idaho and, to a lesser degree, in and around Lewiston in northern Idaho.

Download our free how-to guides!
Backyard Grapes
Selecting Grape Cultivars & Planting Sites in Idaho

Pruning Backyard Grapevines in the First Three Years


Expected yield per vine: 6 to 10 pounds
Age to maturity: 4 years
Productive life: 30+ years
Hardiness (depending on variety): +5 to -25F
Optimum pH: 6.0 – 7.0
Spacing: 5-7 feet apart in rows 10-12 feet apart

GrapesGiven a suitable site, grapes are easy to grow, but more labor intensive than most berry crops due to the amount of pruning, trellising, and training required. Grapes tolerate a wide range of soils, from rather heavy to sandy and acidic to alkaline soils. Best production is on deep, well drained, and neutral to slightly acidic soils.

Climate creates the greatest challenge for grape growers in Idaho. Generally speaking, three types of grapes are available: European (vinifera), American, and hybrids of the two. European grapes are popular for wine, juice, raisin, and table use, but are the least cold hardy of the three types. Examples are ‘Chardonnay,’ ‘Pinot Noir,” and ‘Riesling.’ European grapes are typically cold hardy to about -5 to +10°F and can be difficult to ripen in areas with cool summers. European grapes are risky in all areas of Idaho, but can be grown successfully in the warmest regions of southwestern Idaho in USDA Plant Hardiness Zone 6. Even here, expect vines to be injured or killed by freezing temperatures occasionally. Mulching the base of the trunks with 12 inches of soil or compost from late fall through early spring can help prevent the entire trunk from being killed during cold winters.

American grapes are the most cold hardy types, tolerating winter temperatures of -15 to -25°F. Examples include ‘Concord,’ ‘Delaware,’ and ‘Niagara.’ American varieties are used fresh and for jams, jellies, juices, and wines. American grapes are the most reliably cold hardy throughout the state, normally being considered hardy in USDA Plant Hardiness Zones 5 and 6,  but can be difficult to ripen in northern, central, and southeastern Idaho. Also, grapes have not performed well in many parts of northern Idaho where winter temperatures fluctuate dramatically.

Hybrid grapes represent crosses between European and American species. They are intermediate in cold hardiness, ranging from -15 to +5°F, and include some of the earliest ripening varieties. These varieties are generally used for wines and juices. Examples of hybrid grapes include ‘Aurore,’ ‘De Chaunac,’ ‘Marechal Foch,’ and ‘Verdelet.’ In Idaho, hybrid grapes are best grown in USDA Plant Hardiness Zone 6 and should perform well in the fruit-growing areas of southwestern Idaho and along the lower-elevation Clearwater drainage near Lewiston.

 August 10, 2012
Aug 102012

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

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

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

All Currants and Gooseberries

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

Black Currants

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

Red and White Currants

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


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

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

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

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

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

Selecting a Site

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

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

Pests and Diseases

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

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

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


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

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

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


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

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

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

Weed Control

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

 August 10, 2012
Aug 102012

Blueberries are among the most popular fruits for home and market gardening. Both highbush and lowbush blueberries are native to North America and are used fresh or processed into jams, syrups, compotes, fruit leathers, and pastries. Blueberries are firm and hold their quality well both on the bush and in refrigeration. The fruits are easy to freeze and retain their quality when frozen. Blueberry crops can be harvested two to three years after planting, and reach maximum production in six to eight years. Several types of blueberries are available to gardeners. In Idaho, select varieties adapted to USDA Plant Hardiness Zones 4-6. As a general rule, for long-lived plants like blueberries, select varieties one, or preferably two, zones hardier than your location.

Besides producing fruit, blueberries are attractive in landscapes. The compact bushes are easy to prune and produce brilliant orange to red foliage in autumn. The fruit attracts birds and other animals, making blueberries valuable in wildlife-attracting landscapes. Depending on the variety, mature bushes range from eighteen inches to ten feet in height.

Download our free how-to guide!
Growing Blueberries in the Inland Northwest and Intermountain West


Expected yield:

  • Half-highs 1 to 3 pounds per bush
  • Highbush 8 to 20 pounds per bush

Age to maturity: 6 to 8 years after planting
Productive life: more than 50 years
Hardiness: -15 to -30°F, depending on variety
Optimal pH: 4.2 to 5.2
Exposure: full sun
Plant spacing:

  • Lowbush: 1 foot between plants
  • Half-highs: 2 to 3 feet apart in rows 6 to 8 feet apart
  • Highbush: 4 to 5 feet apart in rows 8 to 10 feet apart
Selecting a Site

Blueberries require acid soils, which greatly limits where they can be grown in Idaho. A soil pH between 4.2 and 5.2 is ideal (pH 7.0 is neutral). Blueberries can be grown, with some challenges, on sites where the pH is as high as 6.0. Blueberries suffer from iron chlorosis on soils with pH values above 6.0 that are common in southern Idaho and scattered throughout the state.

Soils having pH values between 5.5 and 6.0 can be acidified by incorporating sulfur into the soil one or two years before planting blueberries. Soil acidification is not cost effective for large sites or when soil pH values are above 7.0. For small scale production on sites with heavy soils, poor drainage, or alkaline soils, blueberries can be grown in raised beds or containers filled with potting mixes or amended soil.

Sites with cool, moist, well drained loamy sand, sandy loam, and loam soils containing around 3% or more organic matter are best for blueberries. Coarser soils dry out too easily and clay soils inhibit root growth and encourage root rot. Production on silt loam soils is possible, but can be challenging due to poor water drainage. Muck soils and boggy areas are unsuitable for blueberries unless you can create raised beds at least 14 inches above the soil surface. On some sites, increasing soil drainage with buried drainage tiles can improve blueberry production.

While blueberries survive in partial shade, you need full sun exposure to develop good fruit flavor and maintain high yields. Blueberries grown in the shade become tall, spindly, and unproductive, creating bushes that are unattractive and do not tolerate snow loads well.


Blueberries are among the most cold hardy fruits, but there are differences in varieties. The most cold hardy blueberries tolerate temperatures of -35°F or below, and many varieties survive temperatures between -20 and -25°F. Rabbiteye and southern highbush blueberries are not reliably cold hardy in Idaho.

 August 10, 2012
Aug 102012

Berries and grapes are ideally suited to many of Idaho’s growing areas. Regardless of where you live in the state, there are small fruits that you can grow successfully. As with all other crops, however, success largely depends on selecting crops and varieties that are well adapted to your climate and soils.

Blackberries are suited to Idaho’s warmer growing regions, preferably in USDA Plant Hardiness Zone 6, although they can be grown with some success on a few Zone 5 sites. www.usna.usda.gov/Hardzone/hzm-nw1.html. They are best adapted to southwestern Idaho from Mountain Home west and in the Lewiston and Orofino areas of northern Idaho. Even in these locations, select cold hardy, early ripening varieties. You can grow blackberries in other areas, but expect occasional to frequent winter injury and you may have difficulty getting the fruits to ripen before fall frosts.

Blackberries grow best on moderately acidic, deep, well drained soils but will tolerate neutral soils that are somewhat heavier and less well drained than are required for raspberries. If soil drainage is a problem on your site, grow blackberries in raised beds that are about 12 inches high and about four feet wide.

Download our free how-to guide!
Growing Raspberries and Blackberries in the Inland Northwest and IntermountainWest


Expected Yield: 6 to 7 pounds per hill
Age to maturity: 3-4 years
Productive life: 8-12 years
Hardiness: +5 to -20°F, depending on variety
Optimum pH: 6.2 to 6.8
Erect varieties: 5 feet apart in rows 10 to 12 feet apart
Trailing varieties: 5 feet apart in rows 8 to 10 feet apart

Erect Blackberries

Blackberries are divided into two types: erect and trailing. Erect blackberries are generally more cold hardy than trailing types and are better adapted to Idaho. Even the most cold hardy blackberries, however, cannot tolerate temperatures lower than about -20 to -25 °F. Erect blackberries can be grown free-standing, although one or two trellis wires can help keep the bushes more manageable, particularly in snow country. For a list of recommended thorny and thornless blackberry varieties, click here.

Trailing Blackberries

Trailing blackberries (also known as dewberries) include such varieties as ‘Marion,’ ‘Logan,’ ‘Hull,’ ‘Bababerry,’ ‘Tayberry,’ and ‘Tummelberry.’ Trailing blackberries are not reliably cold hardy in Idaho growing conditions. Most are injured or killed by winter temperatures around 0 to +5°F. Although not recommended for commercial production in Idaho, gardeners in the warmest locations can grow trailing blackberries by giving them some extra attention. Details on how to do this, as well as how to select, plant, and care for blackberries in Idaho is in our free guide, Growing Raspberries and Blackberries in the Inland Northwest and Intermountain West.

 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 102012
Farm and Garden Publications

The University of Idaho College of Agricultural and Life Sciences publishes many printed and on-line bulletins and other resources related to farming and gardening. Click here to visit our on-line catalog.

Berry and Grape Grower’s Guides

Growing Blueberries in the Inland Northwest and Intermountain West

Growing Raspberries & Blackberries in the Inland Northwest and Intermountain West

Growing Strawberries in the Inland Northwest and Intermountain West

Growing Western Huckleberries

Backyard Grapes

Selecting Grape Cultivars and Planting Sites in Idaho

Northern Idaho Fertilizer Guide: Blueberries, Raspberries, and Strawberries

 August 10, 2012
Aug 102012

Fruit trees need regular fertilization to remain healthy and productive. How much fertilizer to add depends on the nutrients already available in the soil and the size of the trees. Home gardeners tend to over fertilize their trees, which delays or reduces blossom formation, produces poor yields and fruit quality, and results in vigorous growth of branches and leaves and increased pruning.

Large trees, such as apples on seedling rootstocks, require more nutrients than dwarf trees. Commercial fruit growers have laboratories analyze the leaves in mid summer to determine the nutrient status of the tree. For home gardens, start with the amounts in Table 1 below and watch your trees carefully. If a tree that is old enough to bear a crop produces lush shoots and dark green leaves but few blossoms, you are applying too much nitrogen and/or pruning off too much wood. If growth is slow, stunted, or yellowish, add more nitrogen. Apply fertilizers from early spring through the end of June.

Nitrogen Source Nitrogen Content (%) Planting Year Young Trees (rate per year since planting) Mature Trees (six years or more from planting) (lb)
10-10-10 10 0 6 oz 2
16-16-16 16 0 4 oz 1.5
21-0-0 (ammonium sulfate) 21 0 3 oz 1
Dry manure (other then poultry) 1-2 0 3 lbs 15
Dry poultry manure 3-5 0 1 lb 5

 August 10, 2012
Aug 102012

Some trees will produce more fruits than desirable. With too many fruits on a tree, the fruits tend to be undersized and may be scarred or misshapen by overcrowding. Overbearing can also interfere with the formation of next years flower buds on apples, pears, and other spur-forming fruit trees, and can cause the trees to bear heavily one year and produce few fruits the next.

For apples, pears, peaches, and nectarines, you can remove or thin some of the developing fruits to produce larger, more attractive fruits at harvest. Apples and pears naturally thin themselves, somewhat, in a process called “June drop”. Suddenly hundreds of apparently healthy little fruits drop from the trees. This is a normal process and no cause for alarm. Commercial growers apply chemical sprays to thin their orchards, but hand thinning is best for home gardens. Begin by removing small, weak fruits. Then thin remaining fruits that are tightly clustered to leave one to three inches between fruits. Timing is important. Thin apples within 40 days of full bloom (when 50% or more of the flowers are open). Thin pears within 60 days of full bloom. Thin peaches about 70 days past full bloom.

 August 10, 2012
Aug 102012

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

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

 August 10, 2012
Aug 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

Tree fruits can be very productive and learning to successfully grow fruit may be rewarding to gardeners. In part, success comes from understanding the specifics of your climate and conditions and in selecting the right species and varieties to grow. Some tree fruits, such as apples, pie cherries, and plums, can be grown anywhere in Idaho. Others, like peaches and sweet cherries may not survive or produce in the colder climates and high elevation areas in the state. After planting the best trees, there is still much to learn about caring for fruit trees to enhance production and fruit quality. Discussions on tree care for the predominant fruit crops grown in Idaho are detailed below.

 August 10, 2012
Aug 092012

Fertilizing gardens and landscapes is important to maintain healthy growth and acceptable appearance. Under natural forest conditions, the annual decomposition of leaves, needles and twigs provide a fresh resource of minerals for plants to use. Landscapes usually do not have this nutrient source and are in need of additional minerals since landscape debris is routinely hauled away. There is a plethora of products available to fertilize your plants. It is important to understand basic plant nutrition and fertilizer application principles in order to meet garden fertilizer needs.

Sixteen chemical elements are known to be important to a plant’s growth and survival. Three of these, carbon (C), hydrogen (H) and oxygen (O) are acquired by plants in sufficient quantities from air and water. The other 13 mineral nutrients are acquired by plant roots, which absorb soil minerals dissolved in water. These 13 required mineral nutrients are divided into two groups: macronutrients and micronutrients.

The primary macronutrients are nitrogen (N), phosphorus (P), and potassium (K). Primary macronutrients usually are the ones to be depleted from the soil first because plants use large amounts for growth and survival. Expectations are that some amount of these three nutrients will be needed in the garden every year. The secondary macronutrients are calcium (Ca), magnesium (Mg, and sulfur (S). Fertilization with these nutrients is not always needed. Micronutrients are needed in only very small quantities. The micronutrients are boron (B), copper (Cu), iron (Fe), chloride (Cl), manganese (Mn), molybdenum (Mo) and zinc (Zn). In the high pH soils of southern Idaho, levels of S, Fe, Zn and Mn are often deficient.

Calculating fertilizer application amounts can be a daunting task for the novice gardener. Before fertilizing, you must first determine how much of which nutrient(s) are needed. Determining the amount to apply can be made using historical recommendations found in many garden publications, or using the results of a soil test. The most reliable way is a soil test.  Your local count Extension educator can provide instructions for taking a soil sample.

Next, nutrient content or grade of the fertilizer must be determined. This information is found on the fertilizer package in the form of three numbers. For example, if the fertilizer grade is listed as 10-10-5, the fertilizer contains 10% nitrogen (first number), 10 percent phosphorus (second number), and 5% potassium. If there is a fourth number, it is the percentage of sulfur. The numbers on a fertilizer package are always in the same order, nitrogen-phosphorus-potassium.

The final piece of information that is needed is the land area to be fertilized. Once all of these factors are known, refer to the bulletin Using Soil Tests Results for Garden Fertilization to determine the amount of fertilizer material to apply. For information about fertilizing vegetables, refer to the Soil Preparation for Garden Vegetable section in this web site.

Organic materials are available that can take the place of inorganic fertilizers in the garden. Common forms include blood meal, bone meal, cottonseed meal, sewage sludge, composts, and manures. These fertilizers are usually relatively low in nutrient content compared with conventional formulations and sometimes relatively large quantities need to be applied. Especially when purchased pre-packaged, organic materials can be more expensive than inorganic fertilizers. Colorado State University has published a great discussion on organic fertilizers.

Fertilizing in a landscape is complicated by the fact that different plants have different nutrient requirements. For instance, a lawn uses high amounts of nitrogen while trees generally need very little nitrogen, especially in late summer and fall when applications may induce new growth, which may result in winter cold injury. Managing fertility on other types of plants in Idaho is described in these University of Idaho on-line publications:

By accessing the University of Idaho Resources for Idaho catalog, production and fertilization guides for many additional garden plants can be purchased. Peruse the list at: http://www.cals.uidaho.edu/edComm/catalog.asp?category1=Gardening

Sometimes adding materials to the soil may be beneficial in certain geographical areas while detrimental in other areas. For example, addition of wood ashes and lime make acidic soils more alkaline (higher pH). Consequently, these may be good amendments for northern Idaho’s soils, but not for southern Idaho’s calcareous, alkaline (high in lime) soils.

There are other excellent fertilizer guides on-line. These include:

  • A general discussion about fertilizing a home garden is found in the bulletin, Fertilizing Gardens, published by University of Idaho.
  • A good publication, Fertilizing Your Garden, by Oregon State University that provides information on interpreting soil test results, determining fertilizer needs, and calculating application amounts.
 August 9, 2012
Aug 062012

Assuming you have normally fertile soils, fruit trees are not usually fertilized at the time of planting or during the first growing season. A soil test is your best resource in determining this and helping you to spot trends in fertility over time. Some Idaho soils, however, are deficient in available phosphorus. You can safely add a cupful of steamed bone meal or 0-45-0 fertilizer to the bottom of a planting hole, mix it with a handful of soil, and plant your tree in the hole. Never add fertilizers containing nitrogen, potassium, or boron to planting holes.

 August 6, 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
Aug 062012

Most fruit trees should not require staking when they are planted. As long as a tree remains upright, staking is usually not recommended for free-standing trees. Trunk strength develops as a tree sways in the wind and staking can actually create weak trunks that will not support crop loads. For special production systems, young apple trees can be trained to vertical poles for several years. The slender spindle production system is one example. Apples on dwarfing rootstocks are also sometimes grown on supporting trellis wires. For more information on training systems, refer to Training and Pruning Your Home Orchard.

 August 6, 2012
Aug 062012

When planting a fruit tree, dig a hole large enough to hold all of the roots without cutting any of them off and without bending the roots to fit into the hole. A good strategy is to dig the hole, then build a pyramid-shaped mound in the center of the hole and drape the roots over the mound. Be very careful to ensure that, after the soil has settled, the tree is at the same depth it grew in the nursery. Planting trees too deeply often results in collar and root rot and tree death. Also avoid planting too shallowly, which creates an unstable tree and exposes the collar and roots to excessive drying.

Most fruit trees are sold bare root or may come in pots up to about five gallons in size. Plant bare root trees as described above. Container-grown trees are planted similarly, but take particular care to inspect the root ball after the pot is removed and before planting. Use sharp pruning shears to cut through roots that circle around the root ball or cluster on the bottom of the ball. These could result in eventual girdling of the trunk. Be careful not to drop the tree, twist the trunk or root ball, or break open the root ball. Doing so can break off small feeder roots. Always lift trees from the bottoms of the root balls. Never lift a tree and pot or tree and root ball by the trunk.

A simple rule is that the only soil that goes back into a planting hole is the soil that came out of it. Never replace the soil with compost, peat moss, or potting soil. Never create a blend of soil and compost to fill a planting hole. Doing so creates a barrier at the sides and bottom of the hole that makes it very difficult for water or roots to penetrate to the soil outside the planting hole. Essentially, you create a pot without a hole in the bottom. If you want to amend the soil, before digging, apply up to six inches of amendment and till it into the soil across a five- to ten-foot diameter area centered where the planting hole will be.

 August 6, 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
Aug 062012

Poor soil drainage is a very common cause of problems in a home orchard. Fruit trees on wet soils often fail to thrive, growing slowly, and eventually succumbing to root diseases. Peaches and other stone fruits are especially prone to problems on poorly drained sites.

Gardeners often add compost or other organic matter to heavy soils to improve drainage. In reality, most organic materials have high water-holding capacities and increase drainage problems when added to already heavy soils. Likewise, adding sand to soils on a low-lying site does nothing to improve drainage unless there is a way for water to drain away from the site.

Drainage tiles (buried pipes with holes along the sides) can be used to drain excess water away from a planting site, provided you have a lower-lying area for the water to drain to. For one or a few trees, raised planting beds twelve inches or more high can significantly improve drainage, particularly when heavy native soils are amended with sand or a lighter-textured soil is brought in to create the beds. For a fruit tree, a bed ten feet in diameter should suffice. The beds can be contained within walls or sloped from the centers outward. Apples and pears on dwarfing rootstocks and peach genetic dwarfs have been successfully grown in large (approximately 20 to 50 gallon) containers. Container culture requires great care to ensure adequate irrigation and fertilization, and to prevent girdling roots.

 August 6, 2012
Aug 032012

Please note: Plums and prunes are quarantined by the Idaho Department of Agriculture to prevent the introduction of diseases. Except for the fruit, no plant parts can be imported into Idaho unless they have been grown in a disease-free area and are accompanied by a phytosanitary certificate. Homeowners should purchase their peach and plum stocks at nurseries in Idaho.

Prunes are simply plums that develop high enough sugar concentrations in the fruit to allow the fruit to be dried without spoiling. The trees grow 10 to 20 feet tall and bear fruit three to five years after planting. Cultivars are budded onto rootstocks.

Both European and Japanese cultivars are available. Nearly all Japanese cultivars require cross pollination, as do many European cultivars. As a general rule, plant two or more cultivars close together. Plums are less hardy than apples. Japanese plums are injured at temperatures between -10 and -15 F. European plums are injured at temperatures between -15 and -20 F. Although adaptable to a wide range of soil conditions, the trees perform best on deep, well drained soil.

 August 3, 2012
Aug 032012

Two distinct types of pears varieties are available: standard and Asian. Asian pears are rounder and crisper than standard pears, and are sometimes likened to apples. Pears are less hardy than apples and can suffer freezing injury in some parts of Idaho. The buds and wood of standard pears are typically hardy to about -25°F. Standard pears are widely grown throughout Idaho, although they can be more difficult to grow in central Idaho and the colder parts of southeastern Idaho. Asian pears are less hardy than standard pears and are best suited to the warmer parts of southwestern Idaho. Pear trees grow to about 18 feet tall, but can be kept nearly any size by training and pruning. For artistic gardeners, pears can easily be trained into espaliers or other exotic shapes and can be trained to grow in a narrow wall along trellises or fences, or flat against walls. You can expect your first crop three to five years after planting. Seedling or Old Home rootstocks are commonly used.

Plant on deep, well drained soil and away from frost pockets. While pears tolerate somewhat heavier soils than most other tree fruits, poor drainage can stunt growth, reduce survival, and reduce fruit crops. Neutral to moderately acidic soils are suitable for pears.

Pears require cross pollination, so plant two cultivars close together. Seckel and Bartlett are not cross fertile and will not serve as cross pollinators for each other. Nearly all pear cultivars are susceptible to fire blight disease, particularly in humid climates. Fire blight can be a problem in Idaho, so try to select varieties resistant to the disease. Pear scab is also a problem disease in Idaho.

 August 3, 2012
Aug 032012

Please note: peaches and nectarines are quarantined by the Idaho Department of Agriculture to prevent the introduction of diseases. Except for the fruit, no plant parts can be imported into Idaho from certain places in the united States unless they have been grown in a disease-free area and are accompanied by a phytosanitary certificate. Homeowners should purchase their peach and nectarine trees at nurseries in Idaho.

Nectarines are simply fuzzless peach varieties. Mature trees grow to about 20 feet tall, but can be kept smaller with pruning and training. The trees bear fruit three to four years after planting. Peaches and nectarines are generally poorly adapted to northern, central, and eastern Idaho growing conditions. The trees are sensitive to freezing injury and can be injured or killed at temperatures around -10 to -15°F. Peaches and nectarines also bloom very early in the spring and the flowers are easily damaged by frost.

Varieties of both crops are usually grafted onto seeding rootstocks. Special rootstocks are available, but seldom necessary in Idaho. The trees are naturally small and you can control the size by careful pruning. Peaches and nectarines require well drained, light-textured soil that is neutral to slightly acid. Neither crop tolerates poorly-drained soils well and iron chlorosis develops quickly on soils with pH above 7.0.

Peaches are self-fruitful, as are most nectarines, so you only need to plant one tree or cultivar.

 August 3, 2012
Aug 032012

Sweet Cherries are only marginally cold hardy and the buds can be injured at temperatures near -20°F. Production over the long term is challenging in northern Idaho and questionable, at best, in central and southeastern Idaho. Sweet cherries are grown commercially in the warmer parts of southwestern Idaho. The trees grow to about 25 feet tall and bear fruit about five years after planting. Most varieties require cross pollination, and you must be careful to select varieties that are cross compatible. For a list of sweet cherry varieties recommended for Idaho gardeners, click here.

Tart or pie cherries are more cold hardy than sweet cultivars, and make excellent pastries. The trees grow to about 15 feet tall and bear about three years after planting. Most tart cherries are self-fruitful, so you only need one tree or cultivar. Montmorancy does crop best when planted with another cultivar.

 August 3, 2012
Aug 032012

Please note: Apricots are quarantined by the Idaho Department of Agriculture to prevent the introduction of diseases. Except for the fruit, no plant parts can be imported into Idaho from certain parts of the United States unless they have been grown in a disease-free area and are accompanied by a phytosanitary certificate. Home gardeners should generally purchase their apricot trees from nurseries in Idaho.

The hardiest apricot varieties available in the United States are, reportedly, cold hardy to between -20 and -30°F and are often recommended for USDA Zones 5-8. Varieties developed from Siberian or Mongolian parents are sometimes rated to zones 3 or 4. The trees bloom very early in the spring, making them susceptible to frost injury. Gardeners usually find it difficult to grow apricots in most parts of northern, central, and southeastern Idaho because of frequent frost injury to blossoms and occasional winter kill. Apricots have been grown commercially with limited success around Malad in southeastern Idaho and the crop does well in most parts of southwestern Idaho and around Lewiston.

Apricots are generally self-fruitful, but most experts recommend planting two varieties close together to ensure good fruit set. Varieties are commonly grafted onto apricot or ‘Lovell’ peach seedling rootstocks. The trees grow to about 20 feet tall and should bear their first crop in three to four years. Plant on well drained, light to medium-textured soil that is neutral to slightly acidic. Place the trees on slopes away from frost pockets.

 August 3, 2012
Aug 032012

Apples are among the most cold hardy tree fruits and are well adapted to many Idaho locations. Thousands of cultivars (cultivated varieties) are available and a wide selection of rootstocks makes it possible to grow the trees large or small on many different soils. In fact, perhaps your biggest challenge will be choosing which variety to grow among the more than 13,000 that have been named.

Apples grow and produce best on deep, well drained soils that are neutral to slightly acidic. Production on alkaline soils (pH above 7.0) can be difficult due to a plant disorder called iron chlorosis. Many of the soils in southeastern and southwestern Idaho are alkaline. Simple laboratory tests can help you determine whether your soil is acidic or alkaline and guide you in adjusting the pH with lime or sulfur. Apples bloom early in the spring and are sensitive to frost damage. You will find it best not to plant in a frost pocket or shady location.

When growing on their own roots, apple trees often reach 25 to 30 feet tall. Very tall trees make pest management and fruit harvesting difficult and do not fit into small yards. By grafting or budding a desirable apple variety onto different rootstocks, you can keep mature trees six feet tall or less and even grown them in large pots. In general practice, however, trees in the 10 to 12 foot tall range work best for most gardeners. Malling 9, Malling 26, and Mark are among the most popular dwarfing rootstocks. Malling 27 produces a very small tree that nearly always requires trellising or staking. Other rootstocks, such as Malling 106 and Malling 111 are available for problem soils, but do not reduce tree size much. When these rootstocks are used, growers typically insert an interstem of Malling 9 or Malling 26 to reduce tree size. Many other rootstocks are available, each with particular advantages and disadvantages. Your nursery or garden center should be able to advise you on what root stocks are available.

All apple cultivars require cross pollination to set good crops. Crab apples make good pollinators, as does Golden Delicious. For a list of apples varieties, see the list in the bulletin Growing Tree Fruits in Short-season gardens or in the University of Idaho bulletin Growing Apples.

 August 3, 2012