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.
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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
Given 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.