UNIVERSITY PARK, Pa. -- The trick to growing tomatoes, according to a Penn State gardening specialist, is proper care and preparation.

"You should visit your garden center a few weeks before Memorial Day to pick out the varieties you plan to grow," recommends Peter Ferretti, professor of vegetable crops in the College of Agricultural Sciences. "You can plant earlier than Memorial Day, but you'll need to watch out for frost warnings."

If temperatures dip to frost levels after planting, Ferretti suggests covering the tomato plants with special row covers, paper or cloth, but not plastic. "Plastic covers will cause freezing injury if the plastic touches the plant," he warns.

Ferretti offers the following tomato growth tips:

--Planting. Tomato plants should be planted in early evening, to reduce stress and heat injury from the sun. "Tomatoes need cool, moist conditions after transplanting," Ferretti says. "Set the plant into the ground up to the first set of leaves so the roots will be more stable."

--Stakes or cages. Ferretti recommends either staking or caging the plants as you plant them. "If you wait to stake the plant, you'll end up disturbing or breaking parts of the plant or root system," he says.

--Water immediately. Ferretti says gardeners should use a water-soluble starter solution fertilizer at half the recommended rate. He suggests using about a pint of liquid per plant.

--Fertilizers. "Use a high-phosphorus fertilizer," Ferretti says. "High phosphorus means the middle number on the formula is at least three to four times the other two numbers, such as 12-48-12 or 10-55-10," he says.

--More watering. Ferretti says tomato plants should be watered every week to 10 days, if it has not rained in that time. Gardeners should water so the soil is moist from 6 to 10 inches deep. "Light spray sprinklers will take about an hour to soak the soil thoroughly," he says. "If you use a hose-end sprayer or rose-fan sprinkler, it will take about 10 to 15 minutes of watering. About the time you're running out of patience, that's when the plant has had enough water."

--Tying. Two weeks after planting, the stems should be tied to the stake with soft twine, strips of cloth or yarn.

--Add nutrients. Because central Pennsylvania has calcium-rich soils, gardeners should add magnesium to the soil. Tomatoes require high amounts of magnesium, which can be added by applying high-magnesium limestone, or magnesium-rich dolomitic limestone. The reverse is often true in Bucks and Montgomery counties, so gardners should follow soil test recommendations.

"The bottom leaves of the plant will turn yellow if it needs magnesium," Ferretti says. "When the plant is in a weakened state, early blight, a disease that attacks tomato plants, will hurt the tomato crop."

--Insect and disease control. Ferretti says gardeners can control pests in small gardens by breaking off leaves with evidence of disease or insects. He suggests sealing the affected leaves in plastic bags and throwing them away. If conditions are too far gone, he suggests spraying.

About 40 days after flowering or 65 to 80 days after transplanting, the first tomatoes should appear, Ferretti says. For the best flavor and aroma, gardeners should wait for the tomato to reach full color before picking. "The tomato should be slightly firm, not mushy," he adds.

Even if cooks or gardeners pick a tomato before full ripeness, Ferretti assures that any tomato showing even a trace of color will ripen as long as they aren't refrigerated, but kept at room temperature out of direct sunlight. "How long it takes to ripen depends on size, variety and other factors," he says. "It's best to rely on your own experience."

Ferretti says the plants will continue to produce tomatoes until the first frost. "If you know the frost is coming, go out and pick everything. Those showing color will ripen and the green ones can be fried, or processed into relish."

Ferretti says the following varieties are known for superior taste and aroma:

--Bush Early Girl VFNTA. "A top-quality early tomato," he says. (The VFNTAs means this variety is resistant to Verticillum, Fusarium Wilt, Nematodes and Tobacco Mosaic Virus.) It is probably the largest, earliest, best-tasting variety.

--Big Beef VFNTAsL. (The L means this variety also is resistant to gray leaf spot) Very smooth, flavorful, 10-ounce to 12-ounce fruits.

--Better Boy VFN.

--Delicious. A late beefsteak type tomato with excellent flavor, aroma and large size.

Cherry Tomatoes:

--Super Sweet 100 VF.

--Sungold F. A yellow tomato variety.

Ferretti recommends the variety Husky Gold VF for gardeners growing tomatoes in small patches near patios or in containers. "The tomato is yellow and averages about 2 inches in diameter. The plant is compact with a very sturdy central stalk, so it doesn't require staking," he says.

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EDITORS: Contact Peter Ferretti at 814-863-2313 or pferretti@psu.edu.

Contact: Jeff Mulhollem jjm29@psu.edu 814-863-2719 814-865-1068 fax #171