Tomato suckers or side shoots are the growth that appears in the crotch between the stem and a branch. (See photo at right.) If left to grow, they will become another main stem with branches, flowers, fruit and more suckers of their own.
Why Is Pruning Recommended?
Pruning tomato suckers are sometimes recommended because the resulting new stem is competing for nutrients with the original plant. You may be setting more fruits if you leave the suckers to grow, but the fruits will be smaller and the plant will be more cumbersome. Pruning tomato suckers are really just thinning the plants.
Do I Need to Prune Out Tomato Suckers?
Pruning tomato suckers are never required and many gardeners don’t bother with tomato pruning at all. However even if you prefer to prune your tomatoes, whether to do so or not depends on the type of tomato plant you are growing.
- When You Should Prune Tomato Suckers: Tomatoes are categorized as either determinate or indeterminate, depending on their growth habit. Since indeterminate tomato plants can get extremely large and will keep producing tomatoes all season, they can handle some pruning. If you leave all the suckers to grow, your plants will become heavy and out of control. On the other hand, removing all the suckers will result in a more compact plant, but it will also lessen your tomato yield.
- As long as you have a strong main stem, it’s fine to leave a few suckers on the plant. The general recommendation is to leave 2 or 3 suckers to improve yield but not to let every sucker grow. After that, there is no general agreement.
- Some gardeners like to prune out everything below the first flower cluster to develop a strong central stem. Others prefer to leave a couple of suckers on the lower portion of the plant because these can be easily supported with staking. Then they prune the suckers from the remaining top growth of the plant, to prevent it from becoming too top heavy and falling or splitting.
Tomato pruning is more trial and error than precision, so look at it as an experiment. When you first start pruning, do less rather than more. If you grow the same varieties year after year, you’ll get a feel for how they respond to pruning.
- When Not to Prune Out Tomato Suckers: Determinate type tomatoes don’t really require any pruning at all. Determinate tomatoes tend to be more compact. They reach a certain height and then stop growing. They don’t usually set their fruit until the branches are pretty much fully grown and then they set their fruit all at once. Since no new fruit will be developing after pruning, nothing is gained by pruning.
How and When Do I Prune Out Suckers?
The earlier you prune out the suckers, the easier it is. Small leaves and 2-4" stems can be snapped off with your finger. Stems thicker than a pencil should be cut out with pruners to avoid damaging the plant.