December 16, 2012

Maine Gardener: Plants will reward careful pruners with better berries and grapes

By TOM ATWELL

Raspberries, blackberries, high-bush blueberries and, for some people, grapes are great small fruits for the home garden. They produce every year with not much care, and they taste good.

MORE ON PRUNING

TO SEE a video of David Handley, a small-fruit specialist with the University of Maine Cooperative Extension, teach about pruning, go to umaine.edu/highmoor/videos and click on the one for pruning raspberries or blueberries.

FOR PAMPHLETS, go to umaine.edu/publications and type what you are looking for in the search box.

David Handley, a small-fruit specialist at the University of Maine Cooperative Extension in Monmouth, described how these fruits should be pruned in a recent class at O'Donal's Nursery in Gorham.

You do not prune these plants to get more fruit.

"If you are doing a good job, you will actually decrease the amount of fruit," Handley said. "You want to manage vegetative growth. With that, we are aiming to improve the quality of the fruit."

If the plants produce too much fruit in one year, they often have none the next year because they have no energy left. Pruning allows you to get fruit every year. In producing fewer fruits, the ones you get are likely to be larger.

Also, diseases are more likely to hit these fruits when they are damp. When you remove some of the branches, more wind and sun will hit the remaining branches, and they will dry out more quickly.

Handley told the class that all of this pruning is best done in March when the plants are dormant, because dying vines send nutrients to the roots. It really can be done after late November.

You can prune raspberries and blackberries in the fall -- especially if they are at a summer home and no one will be there in March -- but winter is the best time.

Raspberries and blackberries are biennial plants. The primocane is the first-year cane and on traditional raspberries will produce no fruit. The fruiting cane is the second-year cane.

On everbearing or fall raspberries, the primocane will produce some berries at the top of the cane during the first year. You should cut off the part of the primocane that produced fruit the first year, because it will not produce fruit the second year.

The raspberry bed at the base should be no more than 11/2 to 2 feet wide, Handley said. If you have more than one row, the rows should be 8 feet apart.

"In the summer, you have to remove canes, because they will try to go wider," he said.

If you are careful, you can use a weed wacker.

Once you have narrowed the bed, cut out all the canes that produced fruit the previous year. They will have fruit laterals, have peeling gray bark and be brittle. The good canes will be green and pretty much a single stem.

You leave the ones with the thickest and strongest stems.

"You want to leave only three or four canes per linear foot," Handley said. "They come in clumps, and won't be evenly spread out. If you are not in tears, you haven't taken out enough."

Once you get the base to 1 1/2 to 2 feet wide, you create a trellis consisting of one line of wire about 4 to 4 1/2 feet high on each side of the row, with the trellis wires 3 to 3 1/2 feet apart. You tie the canes to that wire.

You cut the tops of the remaining canes only if they're taller than you so you can easily reach to pick berries.

Blackberries are much like raspberries, except that they will try to grow much taller and have longer fruiting laterals.

For that reason, it is best to prune blackberries into a hill system, with the hills 4 to 5 feet apart in the row, and 5 to 6 canes in each hill.

Because blackberries grow really fast, you'll want to cut the canes that you keep down to about 30 inches high, and cut the fruiting laterals off to about 16 inches.

BLUEBERRIES are in the rhododendron family and produce berries on 1-year-old wood that grows from stems that are 1 to 6 years old.

"You want to have six to 12 canes coming from the ground on each blueberry bush," Handley said.

You cut out the oldest, largest ones when you prune.

"You want the canes to be 1 to 6 years old, not any older. You want to keep the plant in a state of constant adolescence," Handley said.

After you cut the old shoots from the base, you cut the weaker new shoots, saving only a few new ones.

Then you move to the top. You will notice some larger buds that will produce fruit in the coming year, and smaller buds that will produce vegetative matter. You keep the longest, strongest buds, with a good mix of larger fruiting buds and smaller vegetative buds.

If, like me, you have ignored your high-bush blueberries, you can renovate them. If you cut the entire bush right to the ground, it will resprout, creating a new, vigorous bush in three or four years.

If you want to continue getting berries, cut about a third of the bush out each year for three years, until it is back in bounds.

GRAPES are more complicated, and it depends on the kind of grapes you are growing. But for the Concord-style grapes, you want to use a support called a four-arm kniffin.

You create a trellis with poles placed horizontally at 21/2 and 5 feet high, grow the grape vine up in the center, and have 1-year-old branches going out in both directions on each level. You leave two buds on each side to create the next year's vine.

After harvest, you remove the vine that produced the grapes, and pick one of the vines on each side for the next year's fruit.

Tom Atwell has been writing the Maine Gardener column since 2004. He is a freelance writer gardening in Cape Elizabeth and can be contacted at 767-2297 or at:

tomatwell@me.com

 

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