Tuesday, January 20, 2009
Finding the best site for grapes is similar to that for deciduous fruit trees. They prefer: abundant sunlight; deep, fertile, well-drained soils; and a slight slope (preferably south facing) to drain cold air on chilly nights. Grape vines should be planted 6 to 8 feet apart and will need support of some kind. Backyard gardeners often use old-fashioned wooden arbors or the more economical wires stretched between metal fence posts.
At planting, grapes should be pruned back to two buds per vine. Roots should only be pruned if they are damaged. It is important to keep roots moist at all times before and during planting. Planting holes should be wider and deeper than the root system. Spread the roots evenly over a low cone of soil sighting the plant so that it will be at the same soil height as it was when growing at the nursery. Cover the roots with native soil (not amended soil) and bring the finished grade up to the aforementioned planting height. After planting, mulch the vines with compost, well-rotted manure, straw, hay, or leaves to conserve soil moisture.
First year care is critical to grape vine establishment. Irrigate newly planted grapes often enough to keep soil moist but not waterlogged. Do not fertilize grape vines during the first year. The roots are tender and easily burned. Weed control is also important because competition for resources will slow growth.
Newly planted vines should be pruned back leaving only the most vigorous cane. This single cane should be pruned back to leave only two buds. During the first growing season, stake the plant and leave the stake until the trunk can stand without support. Select the most vigorous one and prune off the other closely. Once the cane reaches 60 inches, cut back to 40-50 inches to promote branching below the cut. During the first dormant season, select four lateral cane near the top and prune off all others. The four remaining canes should be pruned back to two buds. These will develop into fruiting canes.
Mature grape vines should be pruned yearly during the dormant period for maximum yields and maintenance of good growth form. To prune, select two vigorous canes near the top of the plant and two farther down. Next to each of these, choose another cane and cut it back to two buds (these are renewal spurs). After selecting four canes and renewal spurs, cut off all others closely. Finally, prune the remaining four canes back to 8-15 buds. These will produce fruit the following year. During the next dormant season, remove the fruiting canes from the previous year and follow the same procedure.
After the first year, irrigate deeply (3-4 ft.) every 2 to 4 weeks. Soil should be allowed to dry out between waterings. Nitrogen fertilizers should be applied to bearing vines. About one-half pound of ammonium sulfate (21% nitrogen) should be applied to each vine. If you choose to grow your grapes organically, then you must know the percent nitrogen of the organic fertilizer you plan to use. Steer manure is usually about 0.5% nitrogen or approximately one-fortieth the amount found in ammonium sulfate. Apply about 20 pounds of steer manure to get the same amount of nitrogen (40 times as much by weight).