Growing Grapes in the Pacific NorthwestLon Rombough
Though the Pacific Northwest produces high quality wines, few people make the connection that great wine also means great grapes. table grapes, that is. Thanks to breeders of American grapes, both in this country and Canada (hang on,that's correct) there are quality table grapes that grow without disease in the NW.
American grapes in this case means grapes with a large percentage of North American grape species in their ancestry. In the past, “American grapes” meant something like “Concord”, which is fine for cooked juice, but fair to poor for many other uses. And Concord has (gasp) seeds.
Some California-style table grapes like Perlette and Flame ripen in the Northwest, but most get powdery mildew, and the fruit often cracks and rots in our wet fall weather. For some years, however, breeders in the eastern U.S. and Canada have been crossing California-type grapes with American grapes to get grapes with the ability to grow in cool, rainy climates. These seedless, and seeded, grapes stand up to wet weather, or even avoid it by ripening before the rain sets in. So they are perfect for the NW. And they resist powdery mildew, our only real vine disease, making them nearly carefree. In many areas of the NW, most of these varieties need only pruning and picking.
Planting, Pruning, & Training GrapesA basic trellis combines a six foot (above ground) steel fence post by the vine(s) with tightly stretched #12 stainless steel wires at 4 and 6 feet to support the vine. Attach the wires to well anchored end posts set in the ground at the ends of the rows.
Plant bare-root vines eight feet apart in the rows in late winter or early spring and mulch them well with compost or other organic matter. Keep the soil moist but not soggy and just let the vine grow the first year to establish it's roots well. The second spring, cut it back to two buds. As the two shoots grow, pinch one back to keep it FROM growing much (it's a “reserve” in case something happens to the other shoot) and train one shoot straight up, tying it loosely to the stake as it grows.
When the new shoot is at least 18 inches above the bottom wire, cut it off just below that bottom wire. Side shoots will grow that are trained horizontally on the wires and will produce the fruiting wood. At this stage you can remove the “spare” shoot from the base of the vine.
The horizontal shoots, which will be the “arms” of the vine, will carry the fruiting wood that will bear the crop.
In winter, prune the two shoots, now called canes, to four feet long. If a cane didn't get that long, cut it back to a short spur with two buds at the main shoot/trunk and try for a new shoot that is straight, the next year. Trying to “extend” an arm that went only halfway makes a kink where it “restarts” that will forever produce unwanted suckers and will be harder to manage.
Next spring, the arms will produce new shoots from each bud, and each shoot will carry from one to three flower clusters. That's more than a young vine can handle, so remove at least three quarters of the flower clusters just as soon as they bloom.
Don't be in a hurry to get a big crop. If the vine has more fruit than it can carry, the fruit will be late to ripen, the quality and sweetness will be less, and the vine itself won't harden it's wood well and shoots may die back in the winter. Six to eight clusters the first year is a safe number on a healthy vine. Add about that many each year until the vine is at full capacity.
Next winter, the canes that arose from the arms will be cut back to short spurs sticking out of the horizontal arm, which is now two years old. Leave no more than two buds on each of the spurs, the first year, and limit the vine to six spurs per arm. In successive years you can leave more buds on the spurs, and even leave more spurs on the shoots as the vine is mature enough to handle them. This system is known as a type of “spur pruning” and will work with most grapes.
A few varieties will fruit better with a different system, called cane pruning. With it, go back to the stage where there were two horizontal canes. After those canes bear a crop, select one of the new canes that grew up near the base of that original cane. It should have at least ten to 15 buds on it. Prune off the old cane and the growth on it, beyond the point where the selected cane is attached. That cane is then tied to the wire to replace the original cane and to bear the next season's crop. Also, select an additional cane as close to the attachment point of the original cane to the trunk, and cut that other cane back to a two bud spur. That spur will produce canes, one of which can be selected as the new fruiting cane the following winter. Thus, every year you replace the old fruiting cane with a new one, and create a spur which produces a new cane to use the following season. As the vine matures, you can leave more canes until the vine has as many as four to six, depending on it's vigor and productivity.
Once you get the knack of pruning grapes (and it must be done every winter) you only have to learn how to pick them. Which will be really easy when you find out how good they are fresh from the vine.