By Marco T. Fonseca
University of Georgia

The Incas of Peru and Mayas of Mexico were growing tomatoes more than 3,000 years ago. When Spanish conquistadors introduced them in Europe in the mid-16th Century, they caught on first in Italy. Can you imagine spaghetti now without tomato sauce?

Tomatoes are popular worldwide now. In North America, though, early settlers regarded them as poisonous plants.

It was centuries before they found favor here. In the early 1900s, U.S. scientists were still trying to convince people of their safety and their value as a source of vitamins A and C.

Tomatoes (Lycopersicon esculentum) are warm-season annual plants. They grow best when days are around 75 degrees and nights about 65. Most people consider the tomato a vegetable. Botanically, though, it's a fruit.

In your garden

Countless tomato cultivars are available now. New ones are being added every year. For your garden, select varieties based on early to late fruiting, insect and disease resistance, fruit size, color and flavor.

In general, there are two types of tomato plants. Determinate, or bush tomato plants, stop growing once they flower. Most commercial varieties are determinate.

Indeterminate plants keep growing until frost or disease gets them. Many of the popular salad and cherry varieties, such as "Better Boy" or "Roma," are indeterminate.

Always choose cultivars with disease resistance. The label will indicate resistance with capital letters such as F (fusarium), V (verticillium), N (nematodes) and T (tobacco mosaic).

The right stuff

Tomatoes require well-drained soils, full sun and good air circulation around each plant and among plants. Don't plant in low areas or where water tends to stand after rain or watering. You can grow tomato plants from direct seed or transplants, but you'll likely be more successful with the latter.

Choose healthy, vigorous transplants. After transplanting, immediately stake or cage the plants to avoid future injuries to branches and root systems. Apply mulch, and pick weeds by hand as well. Tomatoes are extremely sensitive to herbicide damage.

Keeping the soil uniformly moist all season is a must for successful tomato growing. Letting the moisture go back and forth from too wet to too dry will lead to fruit disorders, such as cracking and blossom-end rot, and more disease problems.

Tomatoes are heavy feeders. They require a constant but not excessive supply of nutrients. It's best to base your fertilizer program on a soil test analysis. Any University of Georgia Extension Service county office can provide a soil test.

Once they're harvested, tomatoes may change color, but they won't improve in nutrition or flavor. They can accomplish this only while they're still attached to the plant.

So, pick your tomatoes just before you eat them. Truly vine-ripe tomatoes will have the best taste and the bonus of a higher content of vitamins A and C.

(Marco Fonseca is a horticulturist with the University of Georgia College of Agricultural and Environmental Sciences.)