Sunday, November 10, 1996 - Page updated at 12:00 AM

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Practical Gardener

How To Winter Over Begonias

WSU/King County Cooperative Extension

Q: How can I carry tuberous begonias over the winter?

A: Storing tuberous begonias is not difficult.

Trim stalks and flowers, leaving about 5 inches of stem on the tuber. Lift the tuber gently with a trowel or two spoons.

It's important not to damage or nick the tuber. During summer, it may have expanded, so investigate carefully. Sometimes this is easier to do if it's knocked out of the pot.

Set the tuber, with stems and some soil still on it, in a cool, dry, dark place. Let it dry out. After about a month, the stems will fall off or easily rub off. Don't twist or force.

Bury the tubers in a slightly moist medium, such as peat moss or sawdust. Moisten just enough so that the material is perceptibly damp, but not drippy or soggy. It won't be necessary to re-moisten during the dormant period.

Store in an unheated area, preferably around 40-50 degrees F.

Check the tubers during storage. By early spring, small pinkish buds may show. Pot the tubers before those buds expand into shoots. If shoots are broken or damaged, the begonia's health will be impaired.

Settle the tuber into a pot of potting soil, covering with only about a half-inch of soil. Place the tuber with buds facing up. Keep the soil moist, and if possible, grow in temperatures around 65 degrees (cooler at night).

If all goes well, strong plants with good shoots will be available to set outside in mid-May or early June, when our nighttime temperatures are over 50 degrees.

A good resource on the requirements of various bulbs, corms, and tubers is by John Bryan, "Burpee Expert Gardener on Bulbs." Another is the Park Seed Co. book, "Park's Success with Bulbs."

Q: My apples have been wormy. What can I do this fall to help correct the problem next year? Is there a fall spray?

A: Wormy apples are caused, most commonly, by either the larvae of the codling moth, or by apple maggot. Neither pest should be sprayed in the fall, but there are good choices in garden management for fall that will help.

It's important to identify the difference between the pests.

-- Codling moth is probably more common in Western Washington and is a major pest of apple and pear trees. It will also infest hawthorn and quince fruit.

Fruit damaged by codling moths will show "entry holes" surrounded by brown spongy matter that is forced out of the apple when the larvae feed and burrow to the core.

An infested apple will, when sliced open, show damage around the core area and isolated damage from tunneling. In spite of this, much of the apple is still useful for sliced, cooked dishes such as applesauce.

In late fall, codling-moth larvae settle into whitish-gray, fuzzy cocoons less than an inch long for the winter.

Inside, the codling-moth pupae are brown and about a half-inch long. Hunt for these cocoons in fall in cracks in tree bark or beneath bark scales.

Destroy all apple and leaf debris under the tree. Do not compost, throw it in the trash. Composting temperatures aren't generally high enough to destroy codling moths.

Burying the debris at least 2 feet deep, far from apple or pear trees, is also a possibility.

Dormant sprays, which consist generally of lime sulfur or horticultural spray oils used in late winter before tree growth begins, do not control codling moth, apple maggot or common apple diseases such as scab. They are intended to offer some control for aphids overwintering in the bark, and scale infestations.

-- Apple maggots must be similarly controlled in fall by strict sanitation and disposal of all apple and leaf debris. Maggot damage differs from moth damage in that the fly larvae mine through all the flesh, destroying every part of the apple.

They exit the fruit and spend the winter pupal stage in the soil around the tree. The pupa, often found in the top 2 inches of soil, looks like "a dark brown grain of wheat," as one expert describes it.

For more information, ask your local Cooperative Extension office for publications: EB 1603, "Apple Maggot," EB 1264, "Codling Moth," and EB 0846, "Disease and insect spray schedule for home orchards: apples, pears, and crabapples in Western Washington."

The offices will tell you publication costs and postage. Call (206) 296-3900 for King County Cooperative Extension, (206) 591-7170 for Pierce County Cooperative Extension, and (206) 338-2400 for Snohomish County Cooperative Extension.

Gardening runs Friday in Scene and Sunday in Home/Real Estate, as space is available. It is prepared by Mary Robson, area horticulture agent; Holly Kennell, Washington State University/King County Cooperative Extension agent; Susan Miller, integrated pest-management specialist; and volunteer Master Gardeners.

Copyright (c) 1996 Seattle Times Company, All Rights Reserved.


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