Pruning tomatoes is super-easy, and oh-so-worth-it. Some of the benefits:
- better air circulation around the plants (therefore, fewer disease issues)
- tidy plants (in other words, no tomato jungles)
- clean fruit (since none ever touches the ground)
- easier to harvest the tomatoes
- save garden space, by planting the tomatoes closer together (giving them more vertical space)
- greater productivity of meal-worthy tomatoes
To get the most benefit from pruning tomatoes, the plants should be trellised. Even without pruning, tomatoes benefit greatly from being trellised. There are many ways to go about this, but the most important thing is that they are given enough vertical space.
If you have a 3-foot tall tomato cage - look out! Your tomato plant will very quickly outgrow it! Those cages work best for determinate or dwarf plants. Not for the majority of tomato plants.
In these photos, the tomato plants are clipped onto a string that is suspended from a well-supported overhead wire. A similar method is to tie them (with string) directly onto a tall sturdy stake, or tie them to netting or wire that is stretched between tall stakes.
Ideally, prune your tomatoes once or twice a week. It only takes a few seconds per plant if done every few days, since most suckers will be small and can be pinched out. If you wait any longer than that, you may find yourself dealing with lots of large suckers and witnessing the beginning of a tomato jungle.
Here's why pruning tomatoes is so easy...
As the tomato plants grow taller, they grow predictably in the following pattern:
- leaf branch, with a sucker in the axil
- flower branch
- leaf branch, with a sucker in the axil
- flower branch
As the tomato plant is putting out leaf branches / suckers / flower branches, the main stem just keeps on growing upwards.
So, all you have to do is prune out the suckers, and they are very easy to identify. The sucker always grows in the axil between the "leaf branch" and the main stem.
In the photo below, you can see the sucker between the leaf branch (which is horizontal) and the main stem (which is vertical).
Since the sucker is small, just pinch it out with your thumb and finger. Try to pinch it as close as possible to the base of the sucker.
That is the easiest way to approach it. However, sometimes the suckers get bigger, as in the photo below...
And then they get even bigger! My finger is pointing to the sucker in this photo. You can see that it is still between the leaf branch and the main stem, but quite a bit larger than the suckers in the previous photos.
As the leaf branch grows, it usually bends downwards (as in the photo below). As the sucker grows, it grows upwards (and eventually straight up). This is one way to identify a sucker that is quite large.
When the sucker is large like this, it must be clipped with pruners. Use clean sharp pruners, and make a clean cut as close to the base of the sucker as possible.
It seems that it usually works better to align the pruners with the leaf branch when cutting the sucker. Just be sure to not nick the main stem! (The leaf branch is hiding under the pruners in the photo below.)
Also, it is best to cut off the suckers on a sunny dry day so that the wound skins over quickly. Avoid pruning the tomatoes on damp or rainy days, as this can make the plant more susceptible to disease.
Now, you'll be wondering how to know that you're not cutting off flower clusters when you're pruning the tomato plants. In one sense, you will be cutting off future flower clusters, because all suckers will eventually produce fruit. However, it's better to remove the suckers and let the energy of the plant be directed into flower clusters along the main stem.
Since flower clusters form on the main stem between the leaf branches, you will not accidentally cut off a flower cluster when you are removing a sucker.
Here's a photo of a flower cluster. No sucker or leaf branch near it!
If the tops of the tomatoes are tied to the string / stake once or twice a week (do this when you're spending the few seconds pinching out the suckers!), they will grow nice and straight, and will be very easy to maintain for the summer. Just be sure to tie the string loosely around the main stem, as the stem will grow thicker as the plant continues to grow.
A note about cherry tomatoes... some people prefer to let these plants develop 2 main stems. Cherry tomatoes are extra-vigorous, and can usually support the development of fruit on 2 stems. To do this, simply let one sucker grow near the base of the plant, and it will develop into the 2nd "main stem". Continue to prune out all the rest of the suckers on these two main stems.
If you work with tomatoes long enough, you will get "tomato hands"! As you pinch out suckers, your fingers will become coated with a greenish-black film from the plants. No worries - it washes off! However, it's best to minimize how much you touch the main stem and parts of the plant that will remain, as this coating is part of the plants' protection from disease, etc.
- Side note: the best way to get this film off your hands is to "pre-wash" them with an over-ripe tomato. The film will be gone in seconds.
This pruning method applies only to indeterminate tomatoes. Most tomatoes are indeterminate, which means they keep growing upwards / outwards and setting fruit all season.
If you have determinate plants, you won't need to prune them like this because the plants do not get very tall and usually set most of their fruit at one time. Most determinate plants will be labelled as such.
Have fun pruning, and happy harvesting!