Many vegetable gardens come to an end with the first heavy frost, but this need not be. There are some vegetables that survive well the cool weather of fall and even the cold of winter; the flavor of some is even improved by cold.

Two main vegetable groups can be grown in the fall garden: root crops and greens, including beets, carrots, parsnips, salsify, turnips, rutabagas, winter radishes, kale, collards, broccoli, cauliflower, kohlrabi, Chinese cabbage, Brussels sprouts, and celeriac or turnip-rooted celery.

One of the most important factors in planning a fall garden is the proper time of sowing seeds. Most should be sown in late June, July or August (all dates are for the College Park, Md., area; further north it will be sooner, and further south it will be later).

Fall and winter cabbage, both red and green, grow well from seed planted from mid-June through July. Succulent heads are ready to pick in fall for cooking, coleslaw, sauerkraut or storage in a cool, frost-free place. They keep well and are fresh and tasty into winter.

For something extra delicious, try Chinese cabbage. It grows fast and needs cool weather to head well. Sow seed in late June. It usually yields into late November. It can be served like lettuce or made into coleslaw and is equally good cooked.

Other good salad crops for the fall garden include loosehead and butterhead lettuce, radishes and spinach. All grow so fast you should wait until August to plant them. They stand some frost. If protected with newspapers from the first killing frost, they often can be harvested well into winter.

Winter Bloomsdale spinach is so hardy it will usually live over winter (from a late August sowing) and be ready to supply fresh, tasty greens in the spring. This variety survives, even in severe cold areas, without protection.

Green ice lettuce is especially crisp and tasty in salads; Cherry Belle radish adds zip and color; Bloomsdale spinach gives variety and texture.

Kale and Brussels sprouts really take cold weather. These two vegetables usually taste much better after being frost-bitten, and can be picked from under ice and snow in the winter.

Sow seeds of kale and collards about mid-July. Start Brussels sprouts in peat pots or flats mid-to-late June and transplant to the garden when they are big enough.

Collards and kale often make it through the winter and put on new growth in the spring.

Beets, carrots, turnips and rutabagas provide good eating all fall and well into winter. Sow seeds from mid-June to about the end of July.

The later plantings produce roots just right to store in a cool, dark, frost-free place for winter use. Or store them right in your garden. Don't take them up, just cover the rows in late fall with a thick layer of straw, salt hay or evergreen boughs. Whenever the weather permits, push aside the covering and pull as many roots as you want.

Purple head cauliflower is easy to grow, the heads don't need blanching, and they stay in prime condition for a long time. Sow seed in late June.

Sow seeds of parsley and Swiss chard in late June. Pot up a few plants of parsley for growing on the kitchen windowsill during the winter.

There is one important thing to remember with summer sowing of seeds - keep the ground evenly moist.The weather is often hot, dry and windy so water is necessary with a fine spray to keep the soil damp until seedlings are up and growing well. This often makes the differences between success and failure. Sprouting seeds are thirsty and cannot stand complete drying out, even for a short time.

Many methods of protecting plants from frost have been utilized with varying degrees of success, including plastic film covers, wind breaks, smudge pots, heat burners, wind machines, chemical foam and sprinklings with water.