When you prune tomato plants, more of the plant’s energy is forced into fruit production and less into creating new foliage.
Growing tomatoes is one of the great joys of having a home garden. They aren’t too fussy about where they sit, will grow in sun or light shade and deliver what seems like an endless bounty of fruit until first frost.
Every summer someone asks me, “should I prune my tomatoes”? The answer is, as it many times is in gardening, “that all depends”…
If you have a determinate variety of tomato (bush-type – it will be listed on the plant tag), then the answer to pruning is “no”. Let it grow wild and free. But if you have an indeterminate variety (a vine-type), then “yes”. If you’re not sure what kind you have, the tomato will clearly express its preference within 4 weeks of planting a seedling. If you buy a more mature plant at a nursery, it will be obvious.
I was enlightened to pruning tomatoes when I read this section of Eliot Coleman’s The New Organic Grower: “Prune to a single stem and remove side shoots every few days…the fruit clusters should be pruned to three fruits on the first two clusters and four fruits thereafter”
Mr Coleman grows his tomatoes in a greenhouse and uses overhead supports at eight feet to train the vines upwards. If you can rig up an overhead support, that’s just dandy, but the typical home gardener can get by just fine with a nice tall stake which is at least 6 feet.
Gently tie the tomato’s main vine to the stake right after planting with ribbon, old shoelaces, twine, or other soft material (do not use wire or bread ties, as they cut through the stems). Keep tying the vine to the stake as it grows. The first season of pruning your tomato plants will feel strange, because you’re cutting off a lot of plant, but this actually helps it produce more tomatoes. Remove all suckers as they develop (growths in the crotch between stem and vine), and all non-essential growth, like vines which are spilling out over the raised garden bed or becoming tangled with adjacent bushes. Also “cap” the vine at the top of the stake, because by the time it reaches this point, any new tomatoes it produces most likely won’t ripen by first frost.
See all of my posts with tips on growing tomatoes
As a side note, indeterminate tomatoes grow poorly in cages. By the end of the season they hang over the top and the vine tends to become stressed under the weight of the fruit and prone to breaking. Take it from me, the voice of experience in accidentally growing vine tomatoes in cages: you’ll lose a nice part of your crop come September. Tomato cages are great for determinate varieties, though.
Finally, if you live in an area prone to wet summers, it’s wise to prune the lowest branches on all of your tomato plants. Leaves and stems that touch the ground are extremely prone to developing fungal infections like blight. Keeping the lower 12 inches open allows the stem and leaves to dry much faster after watering.
Speaking of which, don’t water your tomato plants overhead-style with a garden hose. Irrigate your tomatoes with a drip system or hand water with a watering can around the roots only. Keeping the leaves as dry as possible will help keep tomato pests and diseases at bay.
Enjoy your salad, sauce and puree!