Pruning Tomatoes

Tomato pruning can be a confusing subject, partly because much of the available information is contradictory. From not pruning to French pruning, there are lots of variations in between. It mainly comes down to a matter of how you want to spend your tomato sauce gardening time and how you want your garden to look. 

Advantages of pruning tomatoes

1. Allows for better air circulation around plants, keeping them healthier
2. Helps to prevent the spread of disease
3. Makes for a tidier-looking garden, especially important in an ornamental garden
4. Allows more plants to grow in a limited space
5. May result in larger (but fewer) fruit
6. Removed side shoots can be propagated for more free plants
7. Easier to keep plant supported

There are a few drawbacks to pruning tomatoes that should be considered:

1. It takes time and diligence to keep plants pruned.
2. Removing side shoots may reduce overall tomato harvest. In a study by Purdue University, and published in Organic Gardening Magazine, scientists found that removing side shoots was shown to increase the average size of fruit by weight some of the time, but did not increase the total harvest for each individual plant.
3. May introduce disease if tools used are not clean and sharp
4. Pruning side shoots from determinant tomato plants will definitely reduce the amount of fruit produced.

Tomato plants can grow and produce tomatoes just fine without any pruning. However, when tomato plants grow an abundance of extra leaves and branches, the plants may become difficult to support up off the ground. I had several plants that became so unruly that their weight broke the bamboo poles holding them up and they ended up sprawled on the ground resulting in a lot of damaged, slug-eaten tomatoes.

Parts of the tomato plant and pruning

Leaf Branches

Each leaf grows from a branch coming out of the stem. Leaf branches conduct photosynthesis for the plant and protect fruit from sun scald. It will not hurt the plant to snip off a good number of these. I tend to keep the lower 8-12 inches (depending on plant height) of the main stem clear of leaves to improve circulation around the base. I also snip off leaves that turn yellow, get ragged from insect damage, and those that are so big they are touching the ground or interferring with an adjacent plant. 

Fruit branches

These branches grow directly out of the stem-like leaf branches but they contain blossoms that will hopefully turn into fruit. Do not remove any of these that arise from the main stem or you'll have less tomatoes.

Main growing tip

 The main growing tip starts out as a tiny branch with leaves coming out of the topmost joint of the plant. This can be removed in indeterminate tomato plants once they have overgrown their support or when it's late in the season, to allow the plants energy to focus on ripening the existing fruit.

I do not remove the main growing tip on determinate plants. They are predetermined to grow to a specific height and produce a specific number of tomatoes. Removal of the growing tip will sacrifice fruit on determinate tomato plants.

Side shoots

Also known as "suckers" and side stems--these are the tricky ones! Side shoots grow in the joint between a leaf branch and the stem and will grow just like the main stem--they have a growing tip and they produce leaf branches, fruit branches and more side shoots.

The rule that I follow is to leave side shoots alone on determinant plants, since they have a predetermined amount of fruit production that includes fruit from the side shoots. And, limit indeterminant plants to 3 or 4 side shoots and remove the rest as they appear. Also remove any side shoots from the allowed side shoots.

When small, the suckers are easy to remove, they pop right off without need for clippers. Once they've grown too big to pop off, just remove the growing tip of the side shoot--removing the entire shoot can be too much of a shock for the plant.

More thoughts on pruning

Ciscoe Morris, author of Ask Ciscoe--Your Gardening Questions Answered, recommends removing all leaves within five inches of the ground, allowing only 4 extra side shoots or stems per plant and removing all suckers growing from side branches.

In an article published at FineGardening.com Author Frank Ferrandino goes into depth on tomato plant physiology and the benefits of pruning as well as the how-to details. He advocates removal of all leaves and suckers under the first fruiting branch while allowing from one to four stems to grow above it and removing additional side shoots as they appear.

French pruning. In an article published in Organic Gardening Magazine, author William Woys Weaver says that French-pruning tomatoes is a handy way to get larger yields of high-quality tomatoes in a limited amount of space. The method involves pruning tomato vines like grapevines to encourage them to set fruit close to the main stem. French pruning tomatoes works best on indeterminate, medium-size fruit types. Plants are placed about 2 feet apart and each main stem must be supported with a stake. All lower, lateral branches are pruned out as the plant grows leaving a leafy canopy of all the plants together. When plants reach full height, pinch the growing tip to encourage a thicker canopy.

Propagate extra plants. According to author Bob Flowerdew, pruned side shoots can be potted up to make more plants for free. The plants produced are physically mature (NOT seedlings) so they will root, grow and produce fruit at the same time as their parent plant. The side-shoot offspring will be shorter and stockier and will bear the fruit lower down than the parent. This makes them more suitable for a crowded greenhouse. Mr. Flowerdew says that he grows some of these side shoots in small pots to get extra early ripe tomatoes by removing the growing tip and all other buds once one truss of fruit has set. Side shoots that are removed and potted late in the season can be brought indoors to continue producing fruit well into the winter as long as you provide help with pollination.

References

April 2007. "The Perfect Tomato Plan" By Pamela Ruch. Organic Gardening Magazine.

May/June 1999. "Superior Tomatoes in Less Space. An Easy Old-World Pruning Technique Yields Perfect Fruit" by William Woys Weaver. Organic Gardening Magazine.

2007. Ask Ciscoe by Ciscoe Morris. Published by Sasquatch Books.

2002. The No Work Garden by Bob Flowerdew. Published by Laurel Glen.

1998. Bob Flowerdew's Organic Bible. Successful Gardening The Natural Way by Bob Flowerdew. Published by Kyle Cathie Limited.

2007. "Pruning Tomatoes. How to manage your plants for better health and better fruit" by Frank Ferrandino. FineGardening.com. The Taunton Press. 

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