VEGETABLES can be much more tasty if harvested at the best time. They can become tough and poor in flavor if allowed to become over-mature, and they won't keep as well.

Harvest snap beans when the pods are young and succulent and before the seeds are mature. Lima beans should be picked when the seeds are nearly full size but before they turn white. For dry beans let them mature on he plant but harvest before the pods get so dry they shatter.

Older beets may be sweeter but they're also tougher. Dig or pull early beets when they are about the size of a golf ball. For storage, dig them in the fall at maturity and remove the fall at maturity and remove the tops as you harvest them. Do not store bruised specimens.

Oversize sprouts of Brussel sprouts lose some of their unique flavor. Waiting for a light frost or two will actually improve their taste. Pick sprouts from the bottom of the plant first, working up. Harvestable sprouts are bright green, firm and compact, and no more than an inch in diameter. After picking the lower part of the plant, pack dirt around the stalk to promote additional growth on the upper parts.

As it ripens, the cantaloupe stem cracks. When there is a crack all around the stem, it is ready. When the stem is only half cracked, it's a sign the canta loupe will be ripe in a few days.

Enjoy young, small carrots in salads, and let the others grow to full size for winter use. Don't pull them at random; it may attract the carrot fly. Start at one end of the row and work down. Do not let them freeze. They may keep for several months if packed in moist sand and kept in the basement or garage.

Sweet corn has only two or three days of prime taste, so start harvesting it about 18 days after the silk appears. Pick it in the late afternoon when the sugar is at its peak. Check ears before picking. Peel back the husk a little to expose the kernels and pinch one of them until it bleeds. If the fluid is watery, wait two or three more days. If it is milky, pick it. If the corn is not quite ripe, replace the husk. The ear should ripen before insects damage it.

Color is a better guide than size when harvesting eggplants. The shinier the skin, the riper they are.

The younger the greens, the sweeter they are. On most kinds, pick the outer leaves first before they turn yellow or brown. Harvest in the very early morning before daylight respiration begins or plants will wilt immediately. If in doubt, pick while dew is still on the leaves. Pick chard when the blade is between 6 to 10 inches long, spinach when it's no more than 6 inches.

Pick small onions as you need them or wait until the tops dry and fall over.

Wait until the tops are mostly dead to dig up the onions. Don't let the stems rot. Let them dry in the sun for a couple of days and they're ready for storage.

Pick peppers anytime after they're green and firm. Let them grow bigger if you like a thicker stem. Peppers that stay on the vine will turn red but won't get hotter. The more peppers you pick, the more they will grow. Always cut, never break them off.

Dig fresh white potatoes any time after plants have bloomed. These potatoes will have very tender skins, more sugar than starch, and won't store well. For mature potatoes, wait until the vines die back but don't wait too long. The key is to dig potatoes soon after the vines turn yellow from age and begin to lay down.

Q: My lawn had a lot of mushrooms in it this past spring. Can't some of them be eaten?

A: There is an old saying, "There are old mushroom hunters and there are bold mushroom hunters, but there are no old, bold mushroom hunters." So, don't experiment. Eat only those you know to be edible. There are many kinds of wild mushrooms; some are edible, some poisonous. Some edible ones are very similar in appearance to poisonous ones and they may grow side by side. This means you must be able to identify with certainty those you pick and eat.

Q: I have trouble every year trying to grow spinach. Can you offer suggestions?

A: Your soil may be too acid: Have it tested at the state university. Spinach is very sensitive to soils more acid than pH 5.5, and to those above 7.0. The leaves may develop a reddish cast and become stunted if too acid, or yellow if too alkaline.

Q: I'd like to get started with rhubarb. My friends has several plants; can cuttings from them be rooted?

A: A root with a strong bud on it will do nicely. Plant it in early spring, with the bud just below the soil surface. Rhubarb should not be harvested the first year; stalks can be harvested for two or three weeks, the second year, and for eight or 10 weeks thereafter. Roots of rhubarb are listed in many of the mail-order catalogues. McDonald and Valentine are two of the best kinds.

Q: I am plagued with ants in my vegetable garden. How can I get rid of them?

A: With ants, only queen lays eggs. You can step on 100 ants a day and never help the situation. To find her, watch where the ants take their food. If you cannot find the exact site of the nest, apply the insecticide to the general area where you think it might be. Don't let dirty dishes stay out overnight: If one ant finds food, he will tell his comrades where it is.