Most people who are particular about the appearance of their lawns remove the clippings when the grass is cut. In some cases it's a good idea, but in most others it's pure waste.

The clippings of zoysia, Bermuda and St. Augustine grasses almost always should be removed. They decay slowly, and if they're allowed to accumulate thatch is almost certain to develop.

It's different with cool-season lawn grasses such as Kentucky bluegrasses, fescues and rye-grasses. If the grass is rather thin and the clippings can filter down to the soil surface, they decay rapidly.

As the grasses decay, considerable nitrogen, phosphorus and potash are returned to the soil. They analyze roughly at between 5-2-4 and 6-2-3 (nitrogen-phosphorus-potash), according to specialists.

But even more important, the decayed clippings add materially to the improvement of the soil's physical structure and maintenance of its humus supply.

If the grass is rather thick and the clippings cannot get down to the soil level where bacteria will break them down, they should be removed.

Rake them up and add them to the compost pile. Mix the clippings with tree leaves, about 50/50 if possible. Otherwise, they may dry out and pack together and it takes a long time for them to start decomposing.

But these dry, unrotted grass clippings are invaluable for weed control, according to specialists. Spread two to three inches deep around shrubs, they cut off the encroachment of choking grasses and weeds almost completely.

For flower beds, the mulch of grass clippings is absolutely invaluable. Watering and weeding are then hardly needed for the rest of the season.

This mulch should be used only around established plantings, for it keeps bedding plants from sprouting through it as well as it blocks weeds. The ground must be well watered before the mulch is applied.

If it's necessary to fertilize the plants, the layer of matted clippings can be raised up and the fertilizer applied under it.

After the first freeze in late autumn has finished off the weeds, the grass-clipping mulch should be raked off and added to the compost pole.

Q - We have a lovely peach tree which has produced an abundance of peaches for the last 12 years. This year the peaches are many but very small.I would like to start another tree from the one I have but don't know how to go about it. Can you help?

A - There is no way for you to start another tree just like the one you have. In time to come, maybe a year or two, large commercial growers will be able to do it with tissue culture. Your best bet is to buy and plant a new one in the spring, of a variety you like a lot.

Unless peach trees are pruned every year and the fruits thinned, the crop will have poor quality. Fertilizing is also important.

Many gardeners have planted the pits of peaches from their favorite varieties. Sometimes 1 in 100 may be good enough to be worth keeping. But it takes 5 or 6 years to find out.

When you buy the tree you can be fairly certain of what you are getting.

Q - I would like to freeze some of my vine-ripened tomatoes. Do you know a method?

A - Stewed tomatoes can be frozen, so can tomato juice. If the whole tomato is frozen, it will disintegrate when thawed.

If you have a question for Tom Stevenson, write to him at the Weekend section

The Washington Post, 1150 15th St. NW

Washington, D.C. 20071.