Tomatoes Grow Best with Support
The best way to keep tomatoes trim and healthy is to train them onto supports and prune tall-growing kinds during the growing season. (Pruning directs the plants' energy into fruit production rather than producing excess foliage). A stake, trellis, or cage keeps fruits and foliage off the soil and allows air to circulate around the plants, reducing the likelihood of foliage blights. Supported plants are also easier to protect from pests than plants trailing on the ground.
Aphids, whiteflies, hornworms, and even field mice are more visible and more easily controlled when you don't have to battle them in a tangle of ground-hugging vines.
The most common method of trellising is a single stake 6 to 8 feel tall. Pound a 1-by-1 stake or 3/4-inch-diameter bamboo pole a foot or two into the ground. With a soft cloth tie, attach a single vine every 12 inches up the stake. Set stakes 2 to 3 feet apart, 2 feet deep, in rows 3 to 4 feet apart. Single stakes are easy to set up, but they are not wind resistant, and you'll have to prune your vines heavily to keep them trained to 1 stake.
A popular tomato trellis is the tri- or quadrapod, made up of three or four bamboo stakes set together like a miniature tepee. The 3/4-inch diameter 8-foot stakes, set 2 feet apart and leaning to the middle, are lashed together with twine near the top. Tie mature vines to the stakes, or keep them supported and climbing by loosely wrapping a piece of twine around the center vine and then attaching it to the apex of the stake.
A pre-made wire cage can also support plants. With a cage, you spend less time removing suckers, pruning, and training plants, because the plants can grow naturally and support themselves on the sides of the cage. Since you don't prune them, caged tomatoes develop enough foliage to provide adequate shade for ripening fruit and to protect the fruits from sun scald. With this method, the shaded soil also retains more moisture, particularly useful in hot-summer regions.
Pruning Tomato Plants
To prune determinate tomato plants to a single stem, remove the suckers (small shoots) that appear in the leaf axils of the main shoot. 3 to 4 weeks before the first fall frost, prune out the top of the main stem above the uppermost blossom cluster to halt the upward growth and channel energy into ripening the fruit.
More Tips on Tomatoes
Fruit flavor is related to the amount of foliage on the plants, so avoid excessive pruning for best results.
Avoid removing more than a third of a plant's foliage at any one time, because it may shock the plant and hamper its development.
Article provided by the National Gardening Association