Should I prune my tomatoes to get more fruit?
Yes! Tomato pruning will help you get more ripe fruit, not just bushy plants. Although the shiny green leaves of your plants may seem breathtakingly beautiful, you aren’t growing them for looks, but for the juicy tomatoes they can provide for you, and your family.
Tomatoes Come In Two Types
Determinate plants grow to a determined height (usually about three feet) and then stop growing, and redirect all of their energy into leaf and fruit production. They tend to ripen all of their fruit at about the same time. Many of the big beefsteak varieties are in this category.
Determinates will grow pretty well with minimal support and very little tomato pruning. Keeping them caged will mean cleaner fruit, and they should be bottom pruned (#1) and topped at season’s end (#4), otherwise let them side branch as they will.
Indeterminate plants grow vine-like as high or long as they are allowed to. The plants are generally more vigorous and they ripen fruit earlier and continually until the frost gets them. These include most cherry and salad varieties and most heirloom varieties.
I prefer to grow them as a single stemmed plant wrapped around (always clockwise) a tall stake or around bailing twine suspended from a horizontal pole 7 feet off the ground. I build a trellis from the pole with a length of twine dropped every 8 inches, much the same, as you would grow pole beans. I plant and grow the indeterminate tomato plants at 8 inch intervals along the string trellis.
Now, let’s discuss the tomato pruning specifics. Again, only #1 and # 4 apply to determinates, while all apply to indeterminates.
#1 Leafy stems grow directly from the main stem, and above each leaf stem is a flower stem also growing directly out to the main stem. Prune all leaf stems that grow below the first flower stem. That will put the energy into those first fruits. Also pluck any blossoms that bloom before the plant is 12 to 18 inches tall, to insure the plant has a good start before the fruit stage.
#2 At the base of each leaf stem, in the crotch or node, a sucker stem or side branch will grow. These are the ones that should be pinched out on indeterminate varieties; by grabbing the new shoot between thumb and forefinger and snapping it off.
If you want a multi-stemmed plant, let the first sucker grow from the bottom leaf node, and a second or even a third sucker grow from the next nodes up, pinching all the rest as they immerge. Since I prefer single stemmed plants, I pinch all the suckers. That produces a single stemmed plant that puts most of its energy into producing fruit all season long.
There is another style of tomato pruning called the “Missouri Method” which allows the first set of leaves to remain on the sucker stem, pinching out the growth tip just above them. This method provides extra leaf surface to aid in better photosynthesis, but the downside is that each of those extra leaves will also spawn new suckers that will later have to be pinched again. I don’t like all that extra pruning.
#3 As the growing season proceeds it is normal for some of the leaves to yellow and die. Snap or prune these from your plants, as well. This will increase air circulation and sunlight to the rest of the plant, and reduce the incidence of disease.
#4 As you near the end of the tomato season, your plants need to stop producing new fruit and leaves, and concentrate on ripening the fruit already on the vine. You can help the plant to focus by topping or pinching out all of the growth tips. This should be done 30 days before the date of the first expected frost date. In my area, the first frost is usually in the second week of October, so we “top” the tomato plants during the second week in September.
Many gardeners like to tie off their indeterminate tomatoes as they climb. If you do, the ties should be at about one-foot intervals, near a flower stem to better support the fruit. Strips of old cotton (biodegradable) cloth works best.
Using my single stemmed method of wrapping the plant stem clockwise around bailing twine that is secured bottom and top, I have never found it necessary to tie off my plants. I’ve even grown melons, cucumbers and winter squash up those strings without ties. Zucchini, on the other hand, won’t wind around the twine and must be tied off.
When your tomato plant has grown seven, or eight trusses of tomatoes, and reached the top of your stake or trellis it’s time to break off the growing tip. While this may seem a bit harsh, it will encourage more robust produce, than a bunch of teeny tiny tomatoes that lack flavor and luster.
Tomato pruning is a bit of work, but it’s worth it. You’ll have more fruit, ripening earlier, and you’re less likely to suffer the gardeners’ nightmare – a green tomato summer.
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Brenda Larson is the Horticulture Agent for North Carolina Cooperative Extension in Lee County.