Wednesday, June 10, 2009

Prune Tomato Flowers? No!

One question I have been getting a lot of lately: Should I prune off  (snip off, pinch out) the first tomato flowers that appear, in order to get more tomatoes later?

Those early tomato flowers, especially if the weather doesn’t cooperate, will fall all by themselves, thank you. Your assistance is not needed.

Flower drop and tomato fruit set failure can happen in May and June for a number of reasons, including night temperatures below 55; daytime temperatures above 90; excess nitrogen fertilizer, too much shade, too much smog, plants set out too early in spring, or planting the wrong variety for your area (Beefsteaks and San Francisco is not a match made in heaven).

However, by removing those flowers once they are in a situation where they can be pollinated successfully, what is accomplished by removing those flowers? FEWER TOMATOES! And, unless you are trying to stop production, it would be counterproductive to your ultimate goal: shoving that beautiful red orb into the face of your non-gardening neighbor on the Fourth of July, singing, “Nyah, nyah, nyah!”

Wow, where did this fallacy begin? One caller to the radio show offered a clue when he prefaced that question with, “Last night, the local TV Weatherman said…”

Bad move, taking gardening advice from a person who guesses for a living.

Still, that piece of  poor advice must have some historic legs to it. And sure enough, there are many people at Internet gardening forums who are passing on this wrong-headed notion. And as far as I can tell, it’s the result of one gardener reading a piece of university-based research on tomato pruning, and mangling the retelling of that research.

For example, Texas A and M University offers these tips for tomatoes:

"Greenhouse/Hydroponic Tomato Culture (winter)
Single crop rotation-seeded in July or by early August.  Transplants set in greenhouse within 10 to 30 days of seeding.  Harvest begins from 85 to 100 days following date of seeding and continues into June or early July.  Cessation of pollination is six weeks before  termination of the crop.  Growing point is allowed to grow for at least five to seven leaves  above last fruit truss to help prevent sunburned fruit.  Remove flower buds above last fruit  truss to assure no additional fruit set."

Gardener A reads this, and then retells the story to Gardener B, omitting the fact that these were WINTER tomatoes grown in a GREENHOUSE, HYDROPONICALLY. Gardener B then tells Gardener C: “Pruning tomato flower buds is recommended by Texas A and M.” Gardener C then goes online and writes: “Remove flower buds on tomato plants to increase the number of tomatoes.”

Or something like that. And another digital gardening virus is born.

When and how should you prune tomatoes?
Very little, only when necessary, to keep the plants within bounds. If you grow your tomatoes in cages (recommended), you would only need to remove those branches that escape and are threatening to wrap itself around a nearby pepper plant.

If you grow your tomatoes using stakes for support, you may need to do some pruning, according to the University of California:

“Staked tomato plants usually require pruning to a few main stems. At the junction of each leaf and the first main stem, a new shoot will develop. Choose one to three of these shoots, normally at the first and second leaf-stem junction, for the additional main stems. Once a week, pinch off most of the other shoots, called suckers, with your fingers, to keep the plants from becoming to large for their support.”

And, it should be pointed out, that if you follow those pruning guidelines for staked tomatoes, you are sacrificing about 25% of your eventual tomato crop. Yet another good argument to cage, not stake your tomatoes. Cages can be made from sheets or rolls of concrete reinforcement wire with a six inch mesh (the six inch opening makes it easier to reach those tomatoes). The sheets are usually 42” by 84”. Snip off the vertical bars on one of the 42” ends, bend it into a circle, attach the horizontal arms from the snipped end around the other  42” side and you have a tomato cage that’s 42” tall and about 27” in diameter. And it will last for decades. Want a bigger cage? Turn the sheet sideways, snip one of the long ends, bend it into a circle, and you have a cage that’s 84 inches tall and about a foot wide. But I would only do that if I am trying to grow tomatoes as per the instructions of a square foot garden.

Cornell University says hacking back your tomato plants is not necessary:

“…you can grow perfectly fine fruit without pruning your plants. But if you want to prune, here are a few guidelines. For determinate types, there is no need to prune at all. For indeterminate types, allow one, two, or three suckers to grow from the base of the plant. Each of these will become a main stem with lots of flowers and fruit. Prune off all the others suckers and provide the plants with strong support. Research has shown that the best time to remove suckers is when they are about 3 to 4 inches long. For the semi-determinate types, limit your pruning. When the plant is 8 - 10 inches high, look carefully and observe the first flower cluster on the stem. Remove all the suckers below the flower cluster except for the one immediately below the cluster. You may have to go back and give these a second pruning 7 to 10 days later. Remove no more than that or you run the risk of pruning too much. The amount of pruning among these varieties to produce optimum yields varies. Some varieties would do better if you left 2 suckers below the flower cluster. Experiment and see which works best for the variety you are growing.”

The book, 
“Ortho’s All About Tomatoes”, puts in more succinctly, quoting the late Dr. Phillip Minges of Cornell: “Tomato yields per plant may be lowered by pruning. Removing the leaves or shoots does not conserve food for the crop, it tends to reduce the total food supply…use training methods that require little pruning.”

A final hint when searching for garden answers on the Internet. Be leery of advice from gardening forums, unless that advice is linked to a study or research that you can also access. When using a search engine, include the words to identify a prominent agricultural school where the advice is reviewed by multiple parties before publication: UC (University of California), WSU (Washington State), Cornell, TAMU (Texas and M), etc.
For example Googling the phrase “tomato worm UC” will lead you to the University of California Integrated Pest Management website first. If you were to just enter the words, “tomato worm”, well…good luck.

Now, if only I could figure out how to (on my Mac, using Firefox) move the images in Blogger to where I want them....


  1. I never prune, and never remove blooms- and I still have plenty of tomatoes! If people are trying to get more tomatoes, maybe they should just stick in more plants, or like you said, plant varities made for our area.

  2. I have the same problem with images on Blogger, and I'm not using a Mac either. There are people who subscribe to the pruning and flower removal theories, but it's something that I've never put into practice. The inventor of the PVC Tomato Cage concept (Thomas Matkey) always prunes his plants to four leaders, and he seems to enjoy good success with a limited amount of plants. However, last year was not one of his best.


    Purdue university dept. of Horticulture says you should, page 2 second paragraph.

  4. it sounds like Purdue means to remove any flowers from a plant that has yet to be planted in the garden or one that recently was.

  5. My seedlings have been in the ground 2 weeks and some plants are just 8 inches tall and have blossoms. I am in Texas and still have at least 4 full months before the heat kills the plants. Are you sure it is alright to prune back blossoms when a plant is so tiny?

  6. the only time i prune is if the plants flower and they are still in thier pots. case in point - in my early gardening days, i had a plant bloom early and i did not prune the bloom. that plant was essentially stunted until the tomato was picked and then the plant took off. so based upon my, clearly not scientific sample, i get better results if i do prune precocious blooms. once they are planted in the garden beds, they do what they do.

  7. My Roma tomato plants are really leafy. I feel like the tomatoes that are more on the inside aren't going to get enough sun. Should I prune the big green leaves?

    1. It's more important to keep the leaves. Shading the fruit helps prevent sunscald on the tomatoes. And, those leaves aid the photosynthetic process, leading to more tomatoes in the future!

    2. Fruit doesn't need sun.... Remember only green vegetative parts of plants (i.e. leaves) photosynthesize and thus require sunlight.

    3. Erin, that is untrue. Sunlight (and subsequently fruit temperature) absolutely affect ripening.

  8. Thanks Farmer Fred!

  9. Yes I was told to pull the flowers off my tomatoes and peppers and I did!! I guess it was a act of jealousy on there part but since I didn't know any better will I still get more blooms?

  10. good info i agree with your skepticism concerning the plethora of gardening gurus

  11. Excellent information on tomatoes. Definitely a great help for the gardeners. Thanks a lot for sharing the knowledge.

    Impressive write-up, indeed!

  12. When your transplanting, remember..."snip the blooms and it will need more room".
    Dr. Christy

  13. When a plant is producing flowers, it is not building roots and stronger stems, it is trying to reproduce. If your plant is 6in tall and producing flowers, you should pluck them so the plant puts its energy into building stronger roots and stems. If your plant is not planted yet where it will live for the rest of its life, prune the flowers because you don't want its energy leaving the roots and stems. Once your plant is in the ground (or large container) and nice and big, then you can leave the flowers alone. Pruning does NOT sacrifice tomatoes later, it just makes the plant grow bigger so you can have more tomatoes later. Maximize economy before production. This is also how it works for fruit trees- you really don't want fruit your first year or you'll end up with a puny, pathetic fruit tree- so we prune all the blossoms from fruit trees the first year, maybe even the first two. I took years of Botany while getting a degree in Conservation Biology, and also worked in weed management where we developed herbicides specifically based off of this knowledge of how plants grow. This is simply how plants work.

    If you think you're getting good tomatoes from not pruning, have you compared them with a neighbor/friend who prunes? If it works for you, then great, but I wouldn't recommend it on the internet unless you've actually done the experiment yourself (or read a legitimate experiment) to find the most efficient way of growing tomatoes.

  14. There's also the fact to consider- are your tomatoes determinate or indeterminate? The advice I gave was for indeterminate, since we don't bother wasting our time with determinate tomatoes- those guys are better for large scale operations where the whole plant is dug up with all the tomatoes.

  15. I think it also depends on how long your growing season is. If you have a really long growing season, it probably doesn't matter as much? But when you've got a 2-3 month growing season, you really want to get the plants quite large before they make fruit. Again, if not-pruning works for you, then great.

  16. I am no gardener but attempt at it. The temps are cooler this year and we have had a ton of rain. My tomatoe plants have not gotten much bigger but are already producing multiple tomatoes on a few plants. Will this prevent them from filling out and being healthy? Should I remove the tomatoes to allow the plant to grow and fill out? The plants are maybe 15 inches from ground and not very full. Any comments or suggestion appreciated.

  17. I looked this up thinking...that less energy devoted to new growth =faster ripening of existing fruit...and ,i still don`t know thx

  18. I looked this up thinking...that less energy devoted to new growth =faster ripening of existing fruit...and ,i still don`t know thx

  19. the main time I prune is if the plants blossom and they are still in thier pots. a valid example - in my initial cultivating days, I had a plant blossom early and I didn't prune the sprout. that plant was basically hindered until the tomato was picked and afterward the plant took off. so dependent on my, unmistakably not logical example, I improve results in the event that I do prune bright sprouts. whenever they are planted in the nursery beds, they do what they shooter

  20. Best I can fathom is that tomatoes wouldn't prune themselves...why would I? Plant them deep and feed them friendly. They like their space as well. Plenty of light, space to stretch and room to breath. I always have tall heavy producers. Bring on the bacon!!!