Friday, November 14, 2008
A primer on backyard grape-growing
John Arbogast
Landscape consultant John Arbogast answers your questions every Thursday. Send questions about your lawn, garden, plants, or insects to:
Dear John
5102 Greenfield St. SW
Roanoke, Va. 24018
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Q: I’m new at backyard grape growing where I live in western Virginia. I planted a grape plant in spring of 2006 at midpoint of a strong trellis I had built with treated wood end posts set in concrete about 12 to 15 feet apart and then ran heavy wires from the upper part of one post to the other plus more wire about 2 ½ feet beneath that top one. These heavy wires are designed for the grape branches to grow out on. The grape plant has made a lot of growth, and I need to know what to do to control its growth and get plenty of grape clusters. I know that grapes need to be pruned each fall, but I’m wondering if the pruning can be done in the fall? Also, how do I prune them?
A: Annual pruning can be done in the late fall after the grape plant is dormant but before severe freezing weather. Grapes grown in western Virginia are the hardy kinds that can withstand winter temperatures dropping below 10 degrees.
They produce their flowers and then grapes only from buds on wood that grew the year before. I observed this years ago when I was working for Virginia Cooperative Extension in Giles County. I was called to make a “home visit” to see a grower whose grape branches had grown unpruned way up into an adjacent tree and produced grapes where she couldn’t reach them.
If you haven’t done any pruning since you planted, begin now by selecting what will be the trunk and which stem will be the stout shoot growing from the mother plant reaching up to your upper wire. Use garden twist ties to secure the trunk to each of the two wires.
Look for a side branch, which is called an “arm,” that grew out from the trunk and has plenty of plump buds along it growing to the left and an arm to the right from the trunk along each wire. A 1-year-old arm, which can also be called a cane, should have a diameter about the size of a pencil. It’s OK to carefully bend some of the arms or canes to make thinner, 1-year-old arms fit on each wire. Tie them to their supporting wire.
You will now have four arms. Cut the end off each one past the tenth plump bud. This means that you’ll get 40 or slightly fewer clusters formed per plant, which is probably the production limit for making sweet-tasting, nice-sized grapes.
Before you remove all the clutter of unneeded parts, select another small cane from the trunk end of each arm -- or from the trunk near the intersection of the trunk and arm -- and prune it to a short stub having two plump buds. This piece is called a renewal spur that should grow vigorously during the spring and will be in position to be the new fruiting arm or cane for that wire you select during next fall's pruning time.
All other growth on the grape vine should be removed.
You should be left with four fruiting canes, each a year old, one on each arm or wire portion having 10 or slightly fewer plump buds. And you should have four renewal spurs, one on each arm cut back to two plump buds each.
Q: Is pelletized lime better than old-fashioned powdery lime?
A: No, both kinds of lime are effective on unfrozen ground at raising soil pH. Pelletized lime is neater to handle and it shouldn’t create as much dust when applied. Pelletized lime is suitable for use in a rotary spreader.
