The Q&A Archives: Concord Grapes

Question: I have concord grapes easily 40 years old, what should I add to the soil to help promote more fruit production and how and when should pruning be done.

Answer: Grapes are usually pruned in late winter or early spring and are fed once a year (in spring) with a 10-6-4 formulation. Fertilizer can be applied to a single plant at a rate of 1 lb/plant. Be careful not to apply fertilizers containing herbicides (such as some lawn fertilizers) in or near the grapes. Four to six inches of mulch may be applied to help control weeds and conserve soil moistures.

Although there are several systems for training grapes, the four-arm Kniffen system is the most simple. In this system, two horizontal wires are stretched between posts to support the vine. The bottom wire is 36 inches and the top wire is 60 inches above the ground. The young vine is tied to a stake and, as it grows, to the two wires. This ensures a straight trunk for the mature vine.

Mature vines should have four to six canes (each with five to twelve buds) and four to six renewal spurs (each with two buds).

If you're pruninge old and neglected vines, do it in stages. Select a sturdy cane originating near the base of the plant. Cut it back to three to four feet. After this cane completes its second growing season, cut off the old trunk just beyond the attachment of the renewal cane. Old, neglected, or improperly pruned vines usually have too much wood. When pruning, cut as much of the old wood as possible. This encourages the growth of new wood near the main body of the vine.

When pruning, keep in mind that fruit is produced on the current season?s growth, that in turn grows from last season?s wood. Heavy pruning provides the best fruit. Light pruning result in large yields of poor-quality fruit; very heavy pruning produces too much vegetative growth and very little or no fruit. Table, juice, and jelly varieties can have 40 to 60 buds per vine.

Best wishes with your garden!

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