The unusually heavy snowstorm during February caused considerable damage to some evergreen plants, particularly boxwood and Chinese holly. The heavy load of snow and ice that built up on them caused branches to split or break off. Plants under tree branches or eaves of a building were damaged by falling snow. But the snow also protected a lot of plants from severe cold, particularly the flower buds of azaleas and rhododendrons.

Ice, snow and wind injured some shade trees: Limbs broke off and a few split where they were forked. Dead, dying and weak branches should be removed from the wounded tree as soon as is practical.

When snow does accumulate on the branches of evergreen shrubs, it can be removed with an upward sweeping motion of a broom; but don't attempt to remove snow when ice is mixed with it, as it was during the February storm.

Damaged boxwood can be cut back and fertilized in early spring. The same is true of Chinese holly. Pruning can be severe or light, according to the plant's condition. Go easy with it if it is in very poor condition and very little green foliage will be left. The plant needs green leaves to produce food, which is necessary for speedy recovery.

Many boxwood plants that have had little pruning are so compact that little light and air reach the center of the crown. Pruning some of the inner branches will help to open up the plant and admit light to the interior, according to Professor Albert S. Beecher, Virginia Tech horticulturist, and president of the American Boxwood Society.

"After working with boxwood for the last 29 years," he says, "I have come to the firm conviction that lack of proper thinning of boxwood plants is a major contributing factor in much of the dying or declining that has taken place.

"Healthy boxwoods will have a green center and there will be leaves all the way up the stems. In order to obtain this condition, English boxwoods need annual thinning or plucking to allow light and air to reach the center of the crown. Even though the plant appears to be growing exuberantly, this thinning or plucking is needed each year."

Over-fertilizing may injure boxwood plants or lead to excessive pruning to keep the plant within bounds, Beecher says. Usually it is not necessary to fertilize them every year. The plant's requirements will vary depending on the type of boxwood, and soil and growing conditions.

Height can be controlled by shortening the branches in the upper portion. Thinning can be done any time weather is suitable for working outdoors.

Neglected boxwood that have not been thinned for several years can often be rejuvenated by thinning and cutting back a great deal of the top, Beecher says. Drastic cutting-back of plants that have suffered winter injury is beneficial. Heavy pruning should be done in early spring.

Q -- Believe it or not, I'm having trouble raising marigolds. The problem is spider mites. I spray with Kelthane but it is a losing battle. Is there a product you would recommend other than Kelthane ?

A -- Mites rapidly develop resistance to the pesticides used against them. They usually feed on the underside of the leaf and it is hard to do a good spray job on them with marigolds. Try spraying with Dimethoate. It is a systemic and probably will prove effective. But don't spray until you know they are present. Examine the underside of the leaves with a magnifying glass weekly starting when the weather gets hot.

Q -- Do you know of a place where I can purchase small plants of herbs and also scented geraniums ?

A -- Bittersweet Hill Nurseries, Route 424 and Governor's Bridge Road, Davidsonville, Md., has a large selection of herb plants and scented-leaved pelargoniums (geraniums), phone number 301/798-0231.

Q -- We just bought a home. It is a brick building and has ivy climbing over it. Does the ivy do any harm ?

A -- Ivy on a brick building does no damage. On the contrary, is a good thing because it adds highly effective insulation. During the winter, ivy on the north surface will help keep the indoors warmer, and during the summer ivy on the southern wall shelters it from direct rays of the hot summer sun.

Q -- I have a wisteria vine that is trying to wrap itself around a nearby maple tree. Can it be harmful to the tree? The flowers would be lovely way up in the tree but I don't want the vine to hurt it .

A -- The wisteria could seriously damage the tree. When the vine wraps itself completely around the trunk, as the trunk increases in diameter the vine cuts into it and shuts off the movement of food downward to the roots.

Q -- Should evergreen candytuft be cut back when it finishes blooming in the spring ?

A -- Perennial candytuft (Iberis sempervirens) will bloom much better the following spring if it is sheared soon after blooming. Use hedge shears and cut two or three inches off the top including the faded flower stems. Next year's clusters of flowers will develop at the tip ends of new growth. The shearing causes branching and more flowers and also prevents seed formation.

Q -- Can you tell me how to grow peanuts? Where can the seed be purchased? If planted in pots will there be peanuts good enough to eat ?

A -- Peanut plants can be grown in pots but are not likely to produce nuts unless the pot has a depth of at least 12 inches. Full sun is necessary.

They can be grown successfully outdoors in the warmer parts of the country. They need about five months of hot weather for the peanuts to mature properly. They can stand plenty of heat and considerable dry weather. The vine is attractive, bears yellow pea-like flowers.

Peanut seeds are listed in the catalog of Burpee Seeds, Warminster, Pa. 18991, which will be sent free upon request. Instructions accompany the seeds.

PRUNING ROSES -- This Sunday and next, the Potomac Rose Society will hold free demonstrations on pruning roses and display materials recommended for controlling insects and diseases. Both sessions are at 2 o'clock: this Sunday at Brookside Garden, 1500 Glenallen Avenue, Wheaton, and next Sunday at Bon Air Garden, Wilson Boulevard and Lexington Street, Arlington.

TREES FOR $2 -- Marylanders who want to improve the wildlife habitat on their property are getting an assist from the state again this year: a packet of eight seedlings, about a foot tall, for only $2. Each packet includes two dogwoods, two crab apples, two Scotch pines, one autumn olive and one honeysuckle. The packets will be distributed, first-come, first-served, Saturday from 9 to 2. To find out the distribution point nearest you, call 301/269-3683.