Q: I live in a high-rise and would love to grow some herbs and tomatoes on my window sill. Is it practical? I can give them a southern exposure with sunlight.

A: Almost all of the herbs used in cooking can be grown in pots on a sunny window sill, also cocktail tomatoes, small peppers and radishes. Other things can be attempted, and actually the only limit is the amount of space available that gets adequate light.

The big advantage of summer over winter with window sill gardening is the window stays open and the plants do not have to contend with the dry heat that is characteristic of the home during the cold months.

A tomato plant or a petunia has the same basic needs whether it is growing in a pot, tub, bushel basket or in the ground in the garden. It needs enough light, suitable soil, and adequate moisture and nutrients.

The potted plant needs to be watered more often because the soil dries out quickly, and it should be fertilized more often because the roots have only a small area to draw upon for nutrients. The smaller the pot, the more frequent the need for water and fertilizer. If they are not provided when needed, the productive ability of the plant may be seriously impaired.

It is not likely you can make an important reduction in your food bill by growing plants on a window sill but you can have a lot of fun, and some taste treats.

Q: can evergreen candytuft be pruned after it finishes bloomingP I think mine will need it.

A: Perennial candytuft (Iberis sempervirens) should bloom much better next spring if it is cut back soon after if finishes blooming this year. Removal of faded flower stems is particularly beneficial. The pruning causes branching and more flowers, the buds for which will develop at the tip ends of new growth.

Q: Our evergreens were badly damaged last year by bagworms. W ecan see bags now on some of them, probably for a new generation this year. How can we get rid of them?

A: Bagworm hatch from eggs in early June, later in the north, earlier in the south. Each bagworm builds a case or bag around itself and carries this portable house wherever it goes. As the bagworm grows, it adds bits of leaves to the bag.

The bagworm feeds on a great many kinds of plants, but it seems to prefer evergreens such as cedar, spruce and pine. The worms feed on the foliage, all of which may be removed from the branches if the plant is badly infested.

All or parts of the plant may die, depending on how much foliage it loses.

When the bagworm reaches full growth, the bag is about two inches long. The worms change to pupae in September inside the bags. A few days later they change again, this time to adults. The males emerge as small black moths and the females remain in their cases as wingless moths.

After mating, the females produce several dozen eggs, but they do not lay the ggs. Instead, they die, and their bodies serve to house the eggs. The eggs stay over winter inside the bags, safe from most enemies. However, some tiny wasps and flies lay eggs through the case and eventually destroy some bagworms.

To control this pest on a small plant, pick off the bagworm cases before the eggs hatch and burn them. If merely picked and dropped to the ground the eggs will hatch and the worms survive.

On large plants, spray with Sevin (Carbaryl) as soon as possible after the eggs hatch. The larger the bagworms become, the more difficult it is to kill them with insecticides.

Q: What is an oyster plant?

A: Oyster plant is the common name for Salsify, a vegetable, the roots of which taste somewhat like oysters when cooked.

Q: When is the best time to divide rhubarb? We have lots of plants and they are crowded.

A: The best time is late fall or early spring. Rhubarb usually needs to be divided every four or five years.

Q: Will weed seeds in a compost pile stay alive and germinate when I use the compost?

A: Most weed seeds will be killed by the heat that develops when compost materials go through fermentation. Some hard seed, such as morning glory, will come through alive, but most will be killed.