Pruning Grape Vines – Prune According to Vigor

Question: Is the Fall or early Spring the best time to prune grapes?
Answer: Although grapes may be pruned at either of these periods, late Winter or early Spring, after the coldest part of the Winter is over, is the best for this operation.

Late February or early March is considered ideal in the North, but the weather will have to dictate for the various sections of the country. Avoid only very cold days as the canes are then brittle, and break and crack easily, and since the buds snap off easily when hit, be certain to do the pruning before the buds begin to swell.
grapes vines ready for harvest

Adapting Pruning Practices

Adapting the pruning practice to the vigor of the grape vine is the way many northern grape growers determine how many buds to leave at pruning time.

The result has been increased production from vines that formerly were pruned according to habit or rule of thumb.

In commercial vineyards, farm fruit plantings, and even in backyard grape arbors there has been wide diversity of severity of pruning.

The result in some instances was many small straggly stems of small berries with a small amount of new growth for next year’s crop, and in others a few straggly stems of large berries, and “bull” canes 20 feet or more in length.

Pruning Grape Vines – Too Much Too Little

It is not easy to explain intelligently what happens when grape vines are pruned too much or too little. There is, however, a happy medium where a vine will produce an excellent crop and yet make satisfactory cane growth for next year’s crop.

The following method was suggested by horticulturists from New York state, and credit is due these men who developed the practice decades ago. Many Ohio growers benefitted by following their suggestions.

In the first place, the amount of wood removed in the pruning practice and the resulting number of buds left is dependent upon the amount of growth the vine made during the past season. If a large amount of growth was made, the less wood was removed and the more buds were left. If the vine was in poor vigor, fewer buds were left.

To arrive at a common denominator an ordinary spring scale was used to weigh the prunings after they are removed from a vine. This practice of weighing the prunings is not only used in starting the pruning operation, but is used occasionally afterward to check on one’s practice.

The Pruning “Schedule”

The schedule applied to the weight of the prunings is as follows:

Leave 30 buds for the first one pound of prunings and 10 buds additional for each additional pound of prunings.

Thus, if the weight of prunings removed totaled three pounds, one should have left 50 buds on the vine. Or if there was but one pound of prunings removed, the vine should have but 30 buds for next year’s crop. A total of five pounds of prunings would mean 70 buds left.

It may appear that the cart comes before the horse in suggesting that one weigh the prunings after pruning. However, the weighing and adaptation of the weight of prunings is simply a guide to use in becoming familiar with the system.

Growers have reported that they had a certain habit in pruning grapes, and that it was necessary to concentrate on leaving more or less buds as the case may be in the beginning.

By “weighing in” once or twice a day they were able to maintain the practice of pruning according to the vigor of the vine.

It is recognized that varieties differ in need for pruning. Varieties like Concord and Niagara seem well adapted to the initial 30 buds plus 10 for each additional pound of prunings. Probably other varieties should be pruned somewhat more severely.

It also should be emphasized that good soil management practices go along with balanced pruning for good production.

In the beginning, some growers found many vines in the one-pound category, and, in order to make it possible to leave more buds, a good soil management program had to be developed. The use of manure, mulch, and soil building winter cover crops were found most helpful in securing favorable vine growth.

Questions and Answers – Grapes, Pruning and Care

Question: Each year my grapes rot on the vine. The rot seems to start as small tan spots. Later the whole berry rots, turns black and shrivels. What is this and what can be done to stop it?

Answer: You have aptly described black rot, a serious disease of grapes in humid areas. Black rot is caused by a fungus which also produces small, reddish brown spots on the leaves. Blossoms are often blasted.

Control black rot by following a grape spray program. Check with your county agent regarding the recommended schedule for your area

Many states suggest applying a multi-purpose fruit spray containing captan:
(1) when shoots are one inch long,
(2) when shoots are eight to 12 inches long
(3) just before bloom
(4) when fruits are the size of a BB pellet.

It is also important that vines be pruned and retied each spring. Destroy the prunings.There are some varieties which are resistant to black rot. Your county agent or extension horticulturist can advise you about the best varieties to your area.

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