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Topping out tom plants?

My plants were huge last year, probably close to 8'. This year I have been toying with the idea of letting them get to maybe 5' and then taking off anything taller than that. They just become so top heavy and never fruit way up high, I am thinking that maybe forcing the plant to bush out instead of up might work.

So my question is will this work? Or am I going to damage the plants by severely pruning them this way?

If I should just leave them be, then I'll have to build some bigger cages to support them. Those tiny one from HD were pretty much useless last year when the plants got taller than maybe 4'.

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The way my season goes here any flowers that set fruit in early August, but no later, will ripen before frost in October. So I usually pinch off tips above those flower trusses (leaving a few immature leaves above them). Those tips are usually at the top of my 5 ft CRW cages at that time, but that young growth continues to expand as it matures so it will get another foot or so high, but it can be folded back over the cage and doesn't cause too much trouble.

Topping the plants like that will cause more suckers to appear lower down (bush out), but that is usually nonproductive vegatative growth that simply sucks up water. By the time they will fruit they too will have over grown the cages.

Last year I compared staked-pruned plants (1-2 main trunk vines) with unpruned caged plants (6-7 vines/suckers), and fruit count at mid season showed that the staked pruned plants had more than half as many fruits as the 6-7 vine plants). So because the suckers tend to have lower production than the main trunk vines multiple pruned plants (within a single cage) should be more productive than a single "bushy" plant. This would be for large fruited indeterminant varieties, not so much for cherries and paste varieties, which tend to fruit pretty heavily on sucker branches. As for determinate vrieties you don't want to prune them, but they don't tend to over grow cages either.

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Pruning or not...

Greener Thumb

Did you mean that your pruned tomatoes had 1 1/2 times the fruit of the unpruned plants? Or did they have less? I was a little confused.

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I do start pinching out the growing tips on my tomato plants once they get 5-6' tall. This slows them down enough to be more manageable.
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The main trunk vines produce more fruit than the sucker vines. For instance a 6 vine plant consisting of the main trunk and five sucker vines (branches off of the stem) will tend to have about half of the fruit produced on the main vine. So if you have soil space to grow six vines it would be more productive to grow six plants pruned to one vine than one plant allowed to branch into six vines.

Part of this may be because the main trunk starts producing flower trusses before the suckers grow large enough to flower and thus gets a head start, and secondly because the early season flower trusses (in my garden) tend to be much larger than late season trusses. It is not uncomon to see first fruit clusters of 5-10 big beefsteaks while later season fruit clusters are around 1-3 fruit.

The main trunk will often split into two, and later split agin into four trunks. These are different from suckers emerging from leaf axils, and I just leave them on when pruning.

When comparing production of a caged plant having one trunk vines and five sucker vines with a staked plant pruned to one trunk vine (comparing just the fruit produced on the one trunk vine of both), the pruned (staked) plant produces more in most cases. For instance there might be 10 fruit on the trunk of the caged plant (out of 20 fruit on the plant), but the staked plant might have 12-14 fruit.

I did this comparison with about a dozen pairs of plants (two plants each for a dozen different varieties --one staked, one caged), and though there was quite a bit of variability, the pattern I have described was pretty consistent. Enough to convince me to plant four vines for each of my cages this year and prune them. I'll probably grow them up the outside of the cage and tie them off to the wires.

A trunk vine may evenly split into two trunks, and later into four. I do not prune these off because they tend to keep the same production schedule as a single trunk. This was one reason for the variability in my results. A two trunk plant would produce more than a one trunk plant. This could make a staked plant with two or four vines look super productive compared to a the main tunk of a caged plant with one main trunk plus suckers.

Very productive staked plant with two vines (split trunk).

Note the two big fruit clusters on the main trunk vines of this caged plant compared to the smaller clustes produced by the sucker branches of same plant.

Early season production on a pruned plant.

As you can see, if I can grow four plants in the space of one I can take advantage of that early production before disease or disaster hits later in the season.

This might not hold for varieties that tend to produce more fruit later in the season, but those have been few and far between in my garden (Rose and Black Mountain Pink are about the only ones I can recall here).

This might be a good time to ask others if they see too see large initial fruit clusters, as it might just be peculiar to my garden due to climate or my soaking the rootball in high phosphorus bloom booster fertilizer just prior to transplanting into the garden.

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Great info TZ! I usually just let the plants grow but keep a eye on the suckers. When the sucker has its first flowers I cut the vine above the suckers first flowers and get nice tomatoes from the suckers. The suckers actually give more strength to the main plant because they are no longer reaching for the stars like suckers do!
A high nitrogen mix in the soil makes the tomatoes go crazy and give even more suckers with a huge stock and less tomatoes so watch the nitrogen or too much manure!
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mattie g
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Figured I'd jump in on this old thread to get some additional input on my plants now that the days are getting shorter and shorter.

I've got a small garden, but my Brandywines, BKs, and German Queens are absolute monsters - getting upwards of 11' and still growing fast...and with well more than four stems each (despite pruning suckers), which has forced me into all kinds of improvisational staking! I'm at the point where it's getting pretty difficult to keep these things under control, and have thought about the possibility of topping these plants at some point in the next few weeks. I'm expecting a first frost somewhere in mid- to late-October and am now getting a lot of fruit set high up on these plants after all the heat in the height of summer.

Does anyone have input on whether it would be a good idea to do so, and, if so, when might be a best time to give these guys a trim?

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I cut mine back about a month ago. They were at least 7' tall and starting to fold over. Yesterday I went out and had to prune them again as they were probably 7-8' tall again. It has been so hot this year that I haven't had new fruit set in probably 6 weeks. The plants are growing well and the new growth is nice a green. Lots of flowers but no fruit lately.

Well I'm glad I decided to prune yesterday because I found three MASSIVE hornworms buried among the branches! I HATE those things. They promptly got a bath in a bucket of soapy water. I'm now paranoid that I missed a worm or two so I had to go check again twice yesterday. I'm sure I'll be checking daily for the next month too :)

Anyway, during my evening hornworm eradication survey, I found three new fruits that had set on my cherry tomato plant. That thing has been pruned back to almost nothing because of some disease early in the season. So if that one can still produce after being butchered, then there is hope for the others, which are a lot bigger and healthier.

So I say prune away!

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