Q: Is it a good idea to make a second planting of tomatoes in order to be sure of having plenty of them in late summer and early fall?

A: Charles R. O'Dell, Virginia Tech specialist in small fruit and vegetable production, says he doesn't see any advantage in planting a second crop of tomatoes for a better harvest late in the season.

"Rather, I have had best success by not setting tomatoes into soil until soil temperature in the upper two inches has reaches about 55 degrees F., noon reading, he says."

"Setting tropical heat-loving tomato plants in cold soil really sets them back, whereas setting out plants a bit later improves growth rate and subsequent yields.

"Any thermometer with an exposed bulb or mercury-end will do the job for the home gardener.

"High temperatures in August, over about 90 degrees, do reduce fruit set and also cause a hard yellow sunburn shoulder on tomato fruit. Keeping vines well sprayed weekly to retain valuable fruit shading foliage and reducing interior vine temperatures, will improve fruit set and reduce fruit sunburn."

Q: What causes those hard white sections in otherwise good tomatoes?

A: Hard core in tomatoes usually is due to inadequate water during dry weather. Some varieties, such as Beefsteak and strains of Homestead are more susceptible than Better Boy. Manapal and others that bear smaller fruit.

To reduce the problem, mulch your tomatoes and water them thoroughly once a week during dry weather, and plant less susceptible varieties.

Q: I raised Jerusalem artichokes last year and left one in the ground for this year and it is doing well. After I dig them up in the fall, how do I keep them fresh and how long? Can I dig some up during the summer to eat?

A: The best place to store them is in the ground. You can dig and store them in a cool, dark place with moderate humidity or in the refrigerator but they will keep for only about two weeks. Leave them in the ground, mulch them heavily (5 to 6 inches of leaves) to prevent alternate freezing and thawing and when you want some go out and dig them if the ground isn't frozen all winter long. The tubers should not be dug for food until the first heavy frost has killed the tops.

Q: Approximately a year ago we had two thorny locust trees cut down and since then have tried everything we could find to destroy the stumps (approximately 30 inches across) short of buildozing. Some of the remedies we bypassed involve burning the stumps which we understand is contrary to most local ordinances. Can you recommend a reliable remedy?

A: Stumps can be pulled out (by bulldozer), burned out (not recommended), rotted out, or chipped out (by a stump axe - some professional tree service companies have them).

The easiest and cheapest method is to rot them. Cut the stump off at ground level or below, cover it with soil and keep it moist. Nitrogen fertilizer will hasten the rotting process and the rotting also can be hastened by boring several vertical holes in the stump before it is covered.

If sprouts come up from the roots, cut them off immediately and sooner or later the roots will die.

Q: Are castor bean plants effective for getting rid of moles?

A: Moles feed almost entirely on worms and small insects and castor bean plants do not repel them. The best control for moles is the speartype mole trap which can be purchased at most hardware stores. Follow the instructions for use that come with the trap and be persistent.

Q: Why do my onions go to tops instead of forming good bulbs?

A: Your onions are bolting - forming a seed head. Two major reasons account for this. Either you planted a non-adapted variety or the temperature fluctuated widely after the onions started to grow.