You can keep tomato plants from growing too tall by regularly pruning them, providing support such as stakes or cages, and ensuring they receive adequate sunlight and nutrients to encourage healthy growth without excessive stretching.
This means pinching out the growing tips at the top of the plant and stop the plant growing up any further. Stop off at the top of the plant when there are 3-4 (outside grown) and 4-5 (greenhouse grown) trusses, which are layers of flowers.
Once a week, prune about a third of the plant's leaves, starting at the bottom of the plant and working your way up to the top. You can certainly prune less than a third of the leaves, but never do more--that's the golden rule of pruning a tomato (and any other plant).
Cutting the tips of tomato vines stops the growth on that vine. This process of "topping" tomatoes can increase tomato production and provide control over plant growth. Commonly done at the end of the growing season, simple pinching and pruning is all it takes to top tomatoes and improve tomato harvests. (Vid.
Keep repotting until they are in their final pot. This gives the roots plenty of room to grow so that the stem grows normally. Another cause of leggy plants is too much fertilizer in the soil. If the levels of nitrogen are too high, then the seedling will become leggy.
With large-fruited tomato varieties such as ox-heart and beef tomatoes, however, the side shoots should be removed. Even with medium-sized indeterminate tomatoes, we recommend only leaving a maximum of two to three shoots, including the main shoot.
You only need to worry about pruning if you're growing a vining type, aka an indeterminate tomato. Bush tomatoes, or determinate tomatoes, are basically self-pruning because they're meant to only grow to a certain size and then stop.
Pruning. If the crown of your tree is stretching too tall or wide, corrective pruning can help rein it in and size it down for the space available. It's crucial to prune a tree before it becomes a problem because taking away too many branches could cause unnecessary stress.
Often, I put a wood or bamboo stake with each plant to help secure it while it's small. As they mature, the cage and close proximity to other plants will help prop each other up. 2) Use the tall spiral wires and 'single stem' the tomato. I like to then slide one of my old tomato cages over the top for extra support.
Aim to prune plants when the suckers are between 2 and 4 inches long. Determinate tomato plants (those that reach 4 feet tall or so and stop growing) only need to be pruned once. Indeterminate tomatoes can be pruned every couple of weeks as they continue to produce new leaves.
The primary culprit behind tall and spindly tomato seedlings is insufficient light exposure. When tomato plants don't receive enough light, they stretch upward in search of more, resulting in elongated stems and a weak structure.
Most modern determinate tomatoes easily grow 3 to 4 feet tall and indeterminates continue to get taller until frozen in the fall, easily reaching at least 6 feet in height.
As numerous branches begin to flop over the cage from your indeterminate varieties (the type that keeps on growing), take a deep breath and consider cutting some or all of the branches off near the top of their cage support. While pruning stimulates new growth, it takes courage to cut off tomato laden branches.
Only indeterminate tomatoes benefit from topping. If you top a determinate tomato, you'll likely miss out on some of the potential yield.
T-posts will be the most durable stakes and will last you into the following year. The single-stake method works best with determinate tomatoes, which only grow to a certain height and produce most of the fruit in a short window of time.
Called "topping," this type of pruning causes the plant to stop flowering and setting new fruit, and instead directs all sugars to the remaining fruit. This way, the fruit will ripen faster, plus it becomes more likely that the green tomatoes you pick before frost will actually ripen when you bring them indoors.
Water correctly: Do not overwater. The first week tomato plants are in the ground, they need water every day, but back off watering after the first week, slowly weaning the plants down to 1 to 1.5 inches of water per week.
The advantage in removing the lower leaves is that the plants energies go into producing fruit rather than a lot of foliage. Also the lower leaves tend to get powdery mildew so it is good to remove them to stop disease spreading.
I plant the tomatoes in rows, and at the ends of each row I drive steel T-posts into the ground at an oblique angle. Between the plants I push 8-foot-tall 1×1 redwood or bamboo stakes as far into the ground as I can, then push them in farther right after watering, when the soil is soft.
If leggy tomato seedlings do occur, they can often be saved by transplanting them into deeper soil, burying the stem, or providing additional light or support.