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Raspberries: Time to Start Over

By Scott Aker
Special to The Washington Post
Thursday, October 16, 2008

Q Five years ago, I planted a red raspberry bush in the sunniest part of my garden. It grew well but never had more than a dozen or so berries, which always dried up before they matured. I planted some divisions of this bush in a shadier part of the garden, but I'm having the same problem with the fruit. Should I give up on raspberries?

A I suspect your raspberry bushes have a virus that is affecting the fruit crop. Pull them out and plant new, virus-free stock in another location next spring.

Raspberries are not bushes, technically, but brambles. Brambles grow new canes each year that live only two years, a behavior not seen in true shrubs. Varieties fall into two basic categories. The first, called floricanes, fruit in the summer on year-old canes. This makes the pruning regimen complicated. The second type, primocanes, fruit in the fall on new canes. This means that a bramble patch can be mowed to the ground in winter without affecting next year's crop. In addition, they avoid the risk of summer fruit's shriveling in our heat. Larger, sweeter berries tend to grow in cooler conditions. Hence the popularity of primocane raspberries in our climate. Heritage is a popular primocane variety.

Raspberries are best grown in a row at least three feet wide and as long as your appetite for raspberries and the space you have. They can function in the landscape as a low hedge.

Prepare the soil to a depth of at least a foot. Incorporate a two-inch layer of compost or rotted manure, and add lime if the pH of your soil is below 5.5. A soaker hose will allow easy watering as the patch grows.

Plant your raspberries two feet apart. After you have watered the plants thoroughly, mulch them with a three- to four-inch-deep mulch of leaves, good quality mulch or wood chips. The plants may produce a few fruits in their first autumn. Rig a simple trellis system, with wires placed 18 and 36 inches from the ground, to which you can tie the canes.

Raspberries produce a dense thicket of shoots wherever their roots go. Keeping them in bounds is a major chore that becomes more difficult with time. In addition to mowing down all the canes each winter, you will have to cut off many of the sprouts that appear in spring so that individual canes are no less than six inches apart, or the canes will crowd themselves out.

If you grow blackberries or black raspberries nearby, or if wild brambles grow near your garden, they may transmit viruses to your raspberries, resulting in a decline in fruit quality and production over time. If that happens, simply kill your existing raspberries, order new virus-free plants and start over in another location.

I have a fig tree in a large container on my roof terrace. It has been standing in water after recent rains and has begun to lose its leaves. What should I do?

Figs cannot tolerate saturated soil conditions. Do not place a saucer under pots outdoors. This will cause waterlogging. If your fig's container is wet because of standing water on the roof, lift it and place bricks under it to allow drainage. You should also modify the contours of the roof to drain this area, since standing water for long periods may harm the structure.

A large portion of your fig's roots may have rotted, and if this is the case, your fig may not recover. If you notice new growth after raising it from the pool of water, the prognosis is good. Don't fertilize it and water only when the soil is dry.

Scott Aker is a horticulturist at the U.S. National Arboretum.

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