How to Properly Prune Your Tomatoes

Kathryn Fontenot  |  3/2/2012 11:56:08 PM

Diagram 1. How to Prune a Determinate Tomato

Diagram 2. How to Prune an Indeterminate Tomato

Most people who garden love to grow tomatoes. And those who grow tomatoes want good-tasting tomatoes – and a lot of them! One can do many things to ensure (weather permitting) the best-tasting, best-yielding tomatoes. One of the most often overlooked growing practices is pruning tomatoes. Before you start clipping, you’ll need to know what type of tomato you are growing. There are two types, indeterminate and determinate.

Indeterminate tomatoes are those that have a leaf bud as the apical meristem. This means the plant will continue to grow taller as you water and fertilize it. You may have seen these plants grow to heights of 10-12 feet. Determinate tomatoes are shorter than indeterminate because their apical meristem is a flowering bud. Determinate tomatoes generally remain 5 feet tall and under. Both types – indeterminate and determinate – have positive attributes. Indeterminate tomatoes trellis well, and some people claim they produce tomatoes longer. Determinate tomatoes stay shorter and are well suited for the field but also do excellent in containers. You can identify the type of tomato by reading the label. The word determinate or indeterminate should be clearly labeled on the seed pack or small label in the tomato transplant container. A few of the more common determinate tomatoes are Celebrity, Bella Rosa and Mountain Spring. A few of the common indeterminate tomatoes are Early Girl, Better Boy and Fantastic. However, there are thousands of tomato varieties to choose from!

To properly prune a determinate tomato, pinch all suckers from the ground level to the first flower cluster (see diagram 1). A sucker is a small stem that is growing between the main trunk and stem of a tomato. It is usually growing at a 45 degree angle. Pinch the areas shown with red circles around them. You will want to pinch the sucker at the base. Remove the sucker while it is small. If you wait until the suckers are the diameter of a pencil or larger, you run the risk of stripping the outer layer of tissue (the cambium layer) from the main stem. Leaving a large open wound may enable fungus and other unwanted pests to attack your tomato shrub.

To properly prune an indeterminate tomato, prune all suckers from the ground level up to the second flower cluster. See diagram 2. Follow the same instructions as for determinate tomatoes.

Pruning tomatoes encourages larger fruit production at the top of the plant. It also opens up heavy, dense foliage at the bottom of the plant, allowing for better air flow between plants. The open canopy discourages insect and disease populations. Many people are under the impression that suckers do not produce fruit. This isn’t so. But by removing the bottom suckers, you remove the fruit that would weigh down lower branches and rot on the ground.

Now that you know how to properly prune your tomatoes, get growing and have fun.

Some of you might ask “What are other things can I do to ensure (weather permitting) a good stand of tomatoes?" You should first choose tried and true varieties. Look for varieties that have some disease resistance. Avoid planting too close; plant on 18-inch centers. Don’t plant too early and think you’ll be ahead of the game. In south Louisiana, plant spring tomatoes on or after March 15; in north Louisiana, on or after April 1. The soil needs to be a certain temperature before rapid growth will occur, and you don’t want to lose your plants to a late freeze. Use a complete fertilizer in your pot or garden prior to planting, and sidedress with a fertilizer heavy in nitrogen at first and second bloom. If you use calcium nitrate (CaNO3), you’ll prevent some blossom end rot! Don’t over water, but don’t under water. Get at least 1 inch of water per week on your tomato plants. Don’t water heavily when tomatoes are turning color; this will encourage cracking. Instead, water more frequently with smaller amounts of water!

Check with your local AgCenter extension agent to find out if they have local vegetable and fruit field days scheduled. Again, Good Luck and Happy Eating!

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