A tomato is a solar powered sugar factory. For the first month or so, all of the sugar it produces is directed towards 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- 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.

Once flowering commences, all tomato vines must be tied to their supports. Although vigorous, the plants are also easily damaged, so take care in how you tie them and what you use. Cloth strips work well as long as they're not too old and threadbare. Pieces of panty hose cause the least damage to plants, but they're not biodegradable. Twine should be at least 1/8 inch thick, or else it can cut into the tomato stems.

With tomatoes, we want to maximize the efficiency of photosynthesis and minimize the risk of disease. This is best accomplished by ensuring that each leaf has plenty of room and is supported up off the ground. When a tomato plant lies on the ground, or when its growth is extremely dense, many of its leaves are forced into permanent shade, greatly reducing the amount of sugar they produce. If a leaf uses more sugar than it makes, eventually it will yellow and drop off. A pruned and staked plant will produce larger fruit two to three weeks earlier than a prostrate one.