Grapes need full sunlight and high temperatures to ripen, and do best when planted on southern slopes with deep, well-drained soils to avoid standing water in the spring. Vines are planted six to eight feet apart to provide the root system room to spread. To produce plumper fruit and high yield, Concords may be grafted onto a good growth rootstock and planted in soils of optimum fertility.
Summer: Growing and Irrigation
Concord grapes respond favorably to the hot, sunny days of Central Washington’s desert conditions. To keep the vines nourished, juice growers predominately irrigate using impact sprinkler irrigation, but also use drip irrigation, microsprinklers, center pivot systems and rotator sprinklers.
In the Northwest, Concord grapes are harvested from mid-September to late October. Grapes change color long before they are fully mature, so it’s possible to pick the clusters before they have reached their peak in flavor, size and sweetness, if berry color alone is used as a guide. Cool, crisp fall nights typical of the Northwest bring about increased natural sugar and flavor in the fruit. To ensure the fruit is picked at its peak flavor, growers taste the grapes for ripeness and wait for the optimum flavor quality to develop before harvesting, as Concord flavor will not improve in quality once the grapes are harvested. At the peak of ripeness, usually in October, grapes are harvested. Almost 99% of the harvesting today is done by mechanical harvesters, large machines that pass over the vine and literally vibrate the grapes from their stems into troughs.
Winter: Pruning and Training
Each Spring, fruit is produced on the new vine growth sprouting up from the last season’s wood. Heavy pruning, in the late fall or early spring after the vine is dormant for the winter, provides the best fruit. Light pruning results in large yields of poor-quality fruit, while vines that have been overly-pruned produce too much vegetative growth and very little or no fruit. Table, juice and jelly varieties can have 40 to 60 buds per vine, nearly double those of wine varieties.