If you’re growing indeterminate varieties, plan on pruning. You’re liable to end up with a jungly mess otherwise.
For determinate varieties, though, the issue is less clear-cut.
If you don’t prune a determinate, you’ll have plants that are more bushy, and that will produce more but smaller tomatoes. By pruning a determinate, you’ll probably have fewer tomatoes, but each fruit will be larger overall.
Pruning tomato plants is primarily about controlling the number of stems a plant has.
At each leaf node (the junction of the leaf stem and vertical stem) a secondary stem called a sucker will try to grow. If you leave it on the plant, each sucker will grow as an additional stem, producing leaves, stems, and yes – its own suckers.
For a determinate tomato variety growing in a tomato cage, it’ll work fine to have multiple stems. But you might still want to do some pruning to control the density of the foliage.
But you’ll want to restrict an indeterminate variety to a few stems at most – again, depending upon the support system. In my tomato greenhouse, I grow an indeterminate variety and prune off all of the suckers so that there’s just one stem (which is usually over 20 feet in length by the end of the season).
How to Prune Tomato Plants
Pruning tomato plants is very simple. As long as you don’t get behind with the job you don’t even need any tools. Just your thumb and finger will do.
First, identify the sucker you’re going to remove.
Ideally, the sucker will be about 1 to 3 inches in length. If it’s much shorter than an inch, don’t bother with it yet; it will probably just grow back.
Just pinch the base of the sucker between thumb and forefinger, and snap it off by bending it to one side.
Unless you’ve gotten behind with the job and the suckers are large, there’s no need to use pruning shears. And that’s an advantage, because you could potentially spread a disease from one plant to another by using pruning shears.
Here are a few tomato pruning tips:
Prune tomatoes in the morning
Pruning tomato plants in the morning offers 2 advantages:
1) Since the plants are turgid in the cool of morning, the suckers will snap off crisply, cleanly and easily. In the afternoon when the plants are hot and maybe a bit wilty, the sucker will be more inclined to bend than to snap off cleanly.
2) The earlier in the day you prune tomatoes, the more time the wound will have to scab over before nightfall. This will reduce the chances of a disease organism getting established in the wound in the moist nighttime air.
Stay on schedule
Once you’ve decided how you’re going to train and support your tomato plants, prune them as needed every 1 to 2 weeks. That way the pruning will be easier, the wounds from the removed suckers will be smaller, and there’ll be less wasted plant energy in the growth of the removed suckers.
But don’t subject your very young plants to the stress of pruning. Wait until your plants are at least a foot tall before beginning pruning.
Use a bit of caution to prevent spread of disease
Any wound on a plant represents a potential foothold for a disease organism, just as with your skin (something to consider while determining how much you’ll prune). You can minimize the risk by pruning tomatoes only when the plants are dry, and when rain is not expected for the remainder of the day.
It’s also best not to water pruned plants with a sprinkler system that might splash dirt up onto the plants. (In fact, it’s best not to water your tomatoes with a sprinkler at all.)
If you’re growing a lot of tomato plants, you might want to wear some disposable latex gloves while you’re snapping off suckers. (Here's my gloved hand after suckering about 100 plants!)
If you’re doing a lot of suckering, the tomato foliage will leave a dark green stain on your skin that you will not be able to completely remove just by scrubbing with soap.
No need to worry about gloves if you're just doing a small number of plants. Or if you’d like to have a ‘literal’ and semi-permanent green thumb!
It’s an Easy Job
To whatever degree you decide to prune your tomato plants, once you’ve done it a few times you’ll find that it’s a quick and easy job.
Take your time at first so that you’re sure not to remove parts you don’t want to remove. Soon you’ll be able to zip down the row and have your plants pruned in just a few minutes.
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