Growing Grapes in Your Backyard

Return to Main Growing Grapes (table, wine, raisins) in Your Backyard

Do my grapes need fertilizing?

Overview

Given good drainage, grapes are well adapted to a wide range of soils and generally have few nutritional needs. However, in some areas nitrogen, zinc, and potassium may become deficient. If deficiencies do appear applying these nutrients at the right time and in the proper amounts contributes significantly to a successful crop. Table 15.5, linked below, is a simple guide to fertilizer management for grapes.

What about nitrogen? Over-fertilizing with nitrogen can be a problem, whether the nitrogen source is a fertilizer or a leguminous cover crop that fixes nitrogen. Nitrogen fertilizer should be used sparingly on grapes unless a specific deficiency has been diagnosed. Fertilizing with high levels of nitrogen can contribute to excess vegetative vigor in the vines and may reduce fruit set, fruit quality, or both.

How do I apply zinc? If required, zinc can be applied in one of two ways:

For spur-pruned varieties, daubing of a zinc solution onto fresh pruning cuts is easy and works well. During the early winter, when the vines are dormant and the sap is not flowing, prune so that ½ inch of wood is left above the dormant bud. Mix ¼ pound of zinc sulfate (36% metallic zinc content) into a quart of water. Daub the fresh pruning cuts with this solution (keep solution stirred) using a rag or sponge attached to a stick. Soak each cut thoroughly, but do not allow the solution to run down onto the dormant buds. Higher concentrations of this solution may damage buds so do not exceed the suggested rate. Daubing must be done within 3-4 hours of the pruning cuts to be most effective and the vine should not be daubed if the sap flow pushes the daubing solution off the pruning cut.
A second alternative is to spray the leaf foliage in the spring, 1 to 2 weeks prior to bloom or during the bloom period (can be combined with gibberellic acid bloom spray in prescribed varieties). A full coverage spray, usually about ½ gallon of solution per vine is sufficient. Cane pruned varieties, such a Thompson Seedless, are usually sprayed in this manner. The material used for foliage spray is called Neutral Zinc Sulfate. This product contains 52% zinc and is sold under various trade names. The suggested concentration translates to approximately 2 packed, level teaspoons per one gallon (18.2 gm/gallon) of water. This is sufficient to spray 2 mature grape vines. Chelated zinc materials can be purchased through nurseries but have not proven to work as well as neutral zinc sulfate which is also cheaper.

How do I manage the canopy and clusters in the spring?

Associated Links

Publications

Grape Fertilization, Table 15.5 (pdf). UC. Buy Publication

Top of page