Those green tomatoes in your gardens can be salvaged before the first frost ruins them. One way, probably the best, is pull up the plants, roots and all, and hang them upside down in the garage, basement or some other protected place. Pull off the tomatoes as they ripen.

Another method is to pick the larger green ones when frost is expected and wrap them individually with paper. Keep only those that are free of insects and diseases. Check particularly around the base of the stem. Fruit worms often burrow into the tomato at that point.

Grade the fruit according to the degree of maturity. Those that are turning pink won't hold very long.

Don't refrigerate tomatoes until they are ripe. If you do, they will never ripen.

Many people have trouble getting their Christmas cactus to bloom for yuletide. Dr. R. T. Poole, associate physiologist at the Florida Agricultural Research Center, Apopka, who has done three years research on it, says day length and temperature influence blooming.

With a nine-hour day, (kept dark the remaining 15 hours) for six weeks or more, beginning in early October, the plant will start to bloom in 9 to 14 weeks.

Blooming continued for 4 to 8 weeks after the first flower opened, Poole reports.

With a 12-hour day, which starts about Sept. 26, with uninterrupted darkness at night, at night temperatures of 60 degrees, the plant should start to bloom about Dec. 15.

Give the plant very good light during the day, with filtered sunlight preferred until about the middle of November when bright sunlight is fine.

Those who enjoy eating rhubarb can provide now for a crop early in the year. Dig up a clump or two and plant each in a half-bushel basket. Leave the clumps outdoors in the coldest spot available until about the beginning of corner of the cellar or garage where it is about 60 degrees F. Water the clumps when the soil gets dry. You'll be able to harvest the rhubarb in late winter. The leaf stalks, blanched by lack of light, will be milder than those grown outdoors.

If you planted grass seed, the new young grass should be mowed when it is about three inches high. Do not remove more than one inch; in other words, don't cut it lower then two inches.

Too low mowing is to the lawn what overgrazing is to the range; grass consistently deprived of green leat weakens, thins, and becomes supplanted by prostrate weeds like spurge and knotweed. Some of the newer low-growing bluegresses, fescues and perennial ryegrasses will endure mowing at 1 1/2 inches but all usually do better if cut no lower than 2 inches.

Growing a good sweet potato crop in your garden is only half the game. Avoding damage at harvest and curing properly are two important steps in assuring good quality yams.

Sweet potatoes don't mature, so you can harvest them when they are the size you want to use them. Dig them a short time before frost and cure in a warm, moist place, ideally 85 degrees and 90 percent humidity. Then store them at about 55 degrees at as high a humidity as can be maintained.