Growing Grapes - Knowledgebase Question

CANYON LAKE, CA
Question by chet1
February 7, 2006
I WANT TO HAVE A FEW TABLE GRAPE PLANTS IN MY YARD. I WANT SEEDLESS GRAPES. THOMPSON WHITE AND FLAME RED,AND MAYBE MARS OR VENUS BLUE. MY QUESTION IS:WHERE CAN I BUY THESE PLANTS AND WHEN IS THE BEST TIME TO PLANT THEM? WOULD YOU SUGGEST ANY OTHERS? HOW MUCH SPACE IS RECOMMENDED BETWEEN PLANTS? AND, ANYTHING ELSE YOU THINK I SHOULD KNOW.


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Answer from NGA
February 7, 2006

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Grapevines are then sold as bare root plants or in some cases as container stock. Container stock would be planted at the same depth as it grew in the pot and can be planted at any time the ground can be dug. The bare root stock is usually only available in early spring and would be planted at the same depth as it grew originally. These are normally planted in very early spring so they can come out of dormancy naturally with the season. The vines are usually trained to a trellis of desired height such as an arbor in the yard or a series of wires in the field. They are pruned back very hard each winter to stimulate new vine growth and subsequent fruiting. Most vines are also treated with a routine spray program to keep them healthy and productive.

As with all grapes, seedless varieties need full sun with good air drainage. If hardiness is questionable, they can be planted against a south-facing wall.
Soil: Grapes grow well on a wide range of soils but best results are obtained from well-drained sandy loams with a pH of 5.5 to 6.5. They will not tolerate low, wet ground. High pH can be corrected by adding sulfur and thoroughly working it into the soil. The vines are shallow rooted with most of their feeder roots in the top 12 in. of soil.

Irrigation: Regions with 30 inches of annual rainfall usually get enough rain to sustain the plants, unless summer dry spells stretch out past 60 days. In areas with less than that total, supplemental watering may be required. Drip irrigation is economical and satisfactory. In regions of dry summers, young vines may need watering during their first 2 or 4 growing seasons to help establish root systems.

Fertilizing: Nitrogenous fertilizers or complete fertilizers high in nitrogen are recommended. In the first year apply 1/2 lb. of 10-10-10 NPK after planting and then 1/8 lb. of ammonium nitrate in late May and again in early June. Spread the fertilizer in two parallel bands 12 to 14 inches from the trunk. Repeat in the second year, doubling the amounts and lengthening the bands to 48 inches. Thereafter, apply 2 to 4 pounds of the complete fertilizer each March and 1/2 pound of ammonium nitrate each June in a 6 foot long band beginning 1 foot from the tree.

Pruning: Annual pruning must be severe to keep new fruiting wood coming and to prevent vines from becoming tangled masses of unproductive wood. The basic framework of a vine consists of the trunk, permanent arms, and the fruiting spurs. Vines must be pruned each dormant season to maintain this framework. Current season shoots bear the fruit, but to be productive, these shoots must arise from buds set on last season's growth, since shoots from older wood are generally sterile. It is important to leave the correct amount of fruiting wood.

Pruning is basically the same for all trellis systems. Only the arrangement of the fruiting arm is different. Two systems of training are used, the upright or vertical and the overhead or horizontal system. In the upright system, a 3-wire trellis is used, the lower wire being 2 ft. from the ground and the others 2 ft. apart. On the trellis the arms may be horizontal along the wires or fan-shaped from a low trunk. With this system the cane is taken to the top wire and the first year or when vigorous enough, and then topped to make it branch. The resulting laterals are trained along the wire to make the arms.

The overhead trellis provides more bearing surface per vine. The vines form a complete canopy about 7 ft. from the ground. The vines are trained to a single trunk 7 ft. tall with the arms radiating from the top of the trunk like spokes of a wheel. A mature vine will have about 8 arms. During the dormant season each year, cut back all shoot growth of the past summer to fruiting spurs 4 to 5 in. long. Remove shoots entirely that are not needed for spurs of fruiting arms. On young vines leave spurs of one year fruiting wood about 6 in. apart. As the vines get older, they develop clusters of spurs, or spur systems. Generally, thinning of these spurs is necessary after the fourth or fifth fruiting year. This thinning will force new spur growth to replace older spurs.

Grapevines suitable to your area can generally be found in any well stocked nursery or local garden center. Enjoy!

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