The intrinsic vigor and hardiness of tomatoes almost always guarantees a successful harvest. However, the rapid growth of a healthy tomato plant can also lead to problems.
A tomato is a solar-powered sugar factory. For the first month or so, all of the sugar it produces is directed toward new leaf growth. During this stage, tomato plants grow very rapidly, doubling their size every 12 to 15 days. Eventually, the plants make more sugar than the single growing tip can use, which signals the plant to make new branches and to flower.
This usually happens after 10 to 13 leaves have expanded, at which time the plant is 12 to 18 inches tall. In the next few weeks, the entire character of the tomato plant changes. If unsupported, the increasing weight of filling fruit and multiple side branches forces the plant to lie on the ground.
Once the main stem is horizontal, there is an increased tendency to branch. Left to its own devices, a vigorous indeterminate tomato plant can easily cover a 4-foot by 4-foot area with as many as 10 stems, each 3 to 5 feet long. By season’s end, it will be an unsightly, impenetrable, disease-wracked tangle.