Here are some tips on managing your grape crop from Virginia Tech Cooperative Extension.

“Soil Management. Mulching is the preferred soil management practice in home grape planting. Hardwood or softwood bark mulch to a depth of 4 to 6 inches is recommended.

Although grapes are deep-rooted plants, they do not thrive in competition with weeds and grass. If mulch material is unavailable, some cultivation should be done. It should be shallow and only as necessary to eliminate undesired vegetation.

Fertilization. Like all fruit plants, grapes usually require nitrogen fertilization. Except in sandy soils, this element may be the only one needed in the fertilization program. In the home garden, 1 ounce of ammonium nitrate per vine should be applied after growth begins in the spring. Spread the fertilizer in a circle around the plant and 10 to 12 inches from the trunk. Repeat the application about six weeks later. Just before growth begins in the spring of the second year, apply 4 ounces in a 4-foot circle around each vine and about 1 foot from the trunk. Apply the same amount (4 ounces) the third year. A mixed fertilizer, such as 10-10-10, applied at twice the rates, may be substituted where phosphorus and potassium are needed.

Fertilizer applications to mature, bearing vines should be based on the growth and vigor of the plant. If the average cane growth is only 3 feet or less, additional nitrogen may be needed. Where proper pruning is practiced and competition from weeds and grass is kept to a minimum, however, it is doubtful that you will need to go beyond the amount recommended for a 3-year-old vine.

Training and Pruning. Much attention is given to the training and pruning of grapes. To be most productive, they must be trained to a definite system and pruned rather severely. There are several training systems used. Two that are commonly used are the vertical trellis and the overhead arbor. Both of these are satisfactory in the home planting if kept well pruned.

Of the many variations of the vertical trellis, the single trunk, four-arm Kniffin system is the most popular. Posts are set 15 to 20 feet apart and extend 5 feet above the ground. Two wires are stretched between the posts, the lower being about 2 1/2 feet above the ground and the upper at the top of the posts. Set between the posts, the vine is trained to a single trunk with four semi-permanent arms, each cut back to 6 to 10 inches in length. One arm is trained in each direction on the lower wire.

During annual winter pruning, one cane is saved from those that grew from near the base of each arm the previous summer. This cane is cut back to about ten buds. The fruit in the coming season is borne on shoots developing from those buds. Select another cane from each arm, preferably one that grew near the trunk, and cut it back to a short stub having two buds. This is a renewal spur. It should grow vigorously in the spring and be the new fruiting cane selected the following winter. All other growth on the vine should be removed. This leaves four fruiting canes, one on each arm with eight to ten buds each, and four renewal spurs, one on each arm cut back to two buds each.

The same training and pruning techniques may be effectively used in training grapes to the arbor system. The only difference is that the wires supporting the arms are placed overhead and parallel with each other instead of in a horizontal position. Overhead wires are usually placed 6 to 7 feet above the ground.

If an arm dies or for any reason needs to be replaced, choose the largest cane that has grown from the trunk near the base of the dead arm and train it to the trellis wire. To renew the trunk, train a strong shoot from the base of the old trunk to the trellis as though it was the cane of a new vine. Establish the arms in the same manner as for a new vine and cut off the old trunk.

Pruning may be done anytime after the vines become dormant. In areas where there is danger of winter injury, pruning may be delayed until early spring. Vines pruned very late may bleed excessively, but there is no evidence that this is permanently injurious.”

VA Cooperative Extension

Mary Ann Ryan is the Horticulture Program Assistant for Penn State Cooperative Extension - Adams County. Penn State in Adams County is located at 670 Old Harrisburg Road, Gettysburg, PA 17325; phone 334-6271. Penn State is committed to affirmative action, equal opportunity, and the diversity of the workforce.

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