2/12/2012 6:01:00 AM Growing grapes in the high desert
Linda L. Reddick Kingman Area Master Gardener
Grapes may be used fresh, made into jellies or juice or fermented into wine. There is a wide range of flavors among the many varieties. Grapes can be one of the easiest home-garden fruits to grow and one of the most rewarding.
For growing grapes you need a minimum of 140 frost free days, and since here in the high desert (elevations between 3300 and 5000 feet) we have from 200 to 220 frost free growing days, that simply means there is a wide variety of grapes that can be grown.
Purchase Bare Root, or Start Your Own
Grape vines can be purchased from your local garden outlet or nursery, ordered from a catalog or if you are patient, start them from cuttings from a friend or neighbor.
Grapes you purchase commercially are either in containers or bare root. If you choose to try cuttings it will add another year before you will be harvesting your grapes.
December, January early February are the best time to collect cuttings from dormant vines.
Choose cuttings 12-18 inches long that have three to four growth nodes on them. Cut the cane at a 45-degree cut at both the bottom and the top.
Plant the cane with the nodes pointing upwards just like they were growing, keeping at least one node exposed above the soil. Use native soil, in at least a two-gallon container. Water well and secure your cane so it is standing upright.
Grapes should be planted in full-sun locations and well-drained soils. Test the drainage by digging a hole 12 inches wide and 18 inches deep. Fill the hole with water and let it drain. Fill it a second time and observe how long it takes for the water to drain from the hole. If the water drains out in 48 hours or less, the soil has adequate drainage for growing grapes. Vines should be planted at the same depth they were growing.
The planting hole should be wider and deeper than the root system with all rocks and caliche removed. Spread the roots evenly over a low cone of soil setting the plant so that it will be at the same soil height as it was growing.
If vines were grafted, the graft union should be two inches above the ground. Roots should be completely extended out in all directions.
Cover the roots with native soil (not amended soil) and bring the finished grade up to the for-mentioned planting height. After planting, mulch 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, unless you have extremely poor soil, even then use the fertilizer half strength. The roots are tender and easily burned.
Weed control is also important because competition for resources will slow growth. Grapevine roots rapidly grow out several feet during the first two years, so keep the area weed free and well composted.
Newly planted bare root (dormant) vines should be pruned back leaving only the most vigorous cane. This single cane should be pruned back to leave only two or three buds (nodes).
During the first growing season, stake the plant and leave the stake until the trunk can stand without support. 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 canes 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 which will be attached to your arbor or trellis, two on either side.
Structures on which the vines may be trained range from two or more posts set in the ground and strung with two or three horizontal wires (a trellis), to decorative arbors. Bracing should be sufficient to carry the weight of the vines and crop under wind conditions in your area.
Trellis posts should not be more than 20 feet apart and arbor posts not more than 10 feet apart. Wire, (11 or 12 gauge smooth galvanized) should be spaced about two feet apart up the posts or along the top of an arbor. Closer spacing causes excessive shading.
For ease of weed control and to keep fruit up, the lowest wire should be 30 to 36 inches above the ground. Train the permanent trunk to the top wire of the trellis or to the top edge of an arbor.
Mature grape vines should be pruned yearly during the dormant period for maximum yields and to maintain good growth. 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.
After the first year, irrigate deeply (three-four feet) every two to four weeks. Drip irrigation works best for grapes, with two one-gallon drip emitters placed on either side of each plant. Soil should be allowed to dry out between each irrigation. Nitrogen fertilizer should be applied to bearing vines. About one-half pound of ammonium sulfate (21 percent nitrogen) should be applied to each vine, in the early spring and late fall.
Up coming free workshop; "Preparing For Spring Planting," March 3rd, call the University of Arizona Mohave County Extension at (928) 753-3788 for reservations and details.