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Why are my large tomato plants not blooming?

13 years ago

I am growing a couple dozen tomato plants and several varieties of peppers. I'm growing in nothing smaller than 5 gallon buckets, using a variety of soil and soil-less mediums. Pro-mix, gritty mix, etc. I also have four 4x4 beds that I'm growing in.

All my peppers (except some of the really late varieties) are blooming and setting fruit like crazy. The only tomato plants that are flowering and setting fruit are cherry and grape varieties, and a lot of those aren't even going.

I had been feeding with a nitrogen-heavy fish emulsion weekly. I only water when it feels dry. I've switched to ferts to boost my phosphate levels about a week ago. My peppers and some tomatoes just went crazy! Others are just sitting there. They look perfectly healthy.

Varieties that have shown no signs of production:

-Black Cherry

-Black Krim

-Cherokee Purple



All of these were transplanted as seedlings around the same time, in early April. Do these varieties just take a lot longer to flower and fruit?

Am I better off putting them in a spot that is full sun, or more shady? I don't really have a spot that is shady in the evening that I can put them, but I have spots that are shady about 50% of the day (morning). I'd love some input.



Comments (9)

  • 13 years ago
    last modified: 9 years ago

    thanks for the response! I forgot to include the varieties that ARE producing:

    -Roma Grape

    I also left out my Arkansas Travelers from the list of "no flowers yet."

    What I find odd is that all these plants got the same treatment.

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  • 13 years ago
    last modified: 9 years ago

    Did they all get the same potting soil? Some soils have 3 or 4 months worth of fertilizer in them. Could you have used one of those and then added more?

  • 13 years ago
    last modified: 9 years ago

    Oops, I forgot. Arkansas Traveler is a late season tomato.

  • 13 years ago
    last modified: 9 years ago


    There are several possible reasons.

    Tomato plants are individuals and not clones, so they all will not act the same as one another. They'll have their own individual responses to the conditions in which they're living. Once you've grown tomatoes for a while, you'll even notice that a specific variety performs differently (and even tastes differently) in different years.

    You cannot compare peppers to tomatoes because they are not exactly the same. Hot peppers, in particular, are not as affected by the heat/humidity as tomatoes are, for example, so they tend to set fruit all summer long. Some sweet peppers do so as well, although some of them slow down in the worst of the summer heat.

    Fish Emulsion isn't really high nitrogen, or at least not high enough to impede flowering in and of itself. Most fish emulsions have an NPK ratio of either 5-1-1 or 5-2-2, which hardly is an exceptionally high amount of nitrogen.

    Is the issue you're seeing that no flowers are forming at all or is it that flowers are forming and dropping off because fertilization is not occurring? That's a key issue because they are separate problems.

    If no flowers are forming, then the plants are not mature enough to set fruit and carry a load or there is too much nitrogen (which means your mix has too much nitro because fish emulsion alone wouldn't do it) or some other sort of nutritional imbalance. Or, it could mean they are not receiving enough hours per day of sunlight.

    If flowers are forming and falling off unpollinated, that's blossom drop and it generally is related to high heat/high humidity. The larger the fruit a plant produces, the more that flowering/fruitset seems to be impacted negatively by heat heat/high humidity. So, even when the heat and humidity are high, many of the bite-size tomatoes (whether they're classified as cherry, grape, currant, plum or pear-shaped) flower and set fruit just fine, but a few of them do not. Varieties that produce really large fruit often do not flower or set fruit well in high heat and high humidity. Some varieties that produce smaller slicer or saladette types will set fruit at high temps almost as well as the bite-sized ones do.

    Every tomato variety reacts differently, so some may have blossom drop when nighttime lows are exceeding 72 degrees, but others might not see blossom drop until nighttime lows are exceeding 75. The same is true with high temps. For some varieties, 92 degrees appears to be the point at which fertilization ceases but for others it might be 95 degrees. Then, if you have high humidity, that can make pollen sticky so that it clumps together and does not shed from the anthers like it should. Conversely, in very low relative humidity you may see fruit set even at high temperatures.

    My best guess is that part of the problem is the varieties you chose...most are mid-season or late-season and not early season. So, they flower and fruit a bit later than tomatoes with a shorter DTM. Keep in mind that DTMs are estimates only and your actual results may vary quite a bit from the DTMs. Part of the problem is undoubtedly the high humidity and/or high heat or some combination thereof.

    If you are getting blossoms and they then abort without setting fruit, it could be the heat or the humidity, but it also could be poor air flow. If the pollen is a little sticky and isn't shedding from the anthers, you can help it along with thumping each individual blossom or by gently shaking the tomato cage.

    Also, while you don't want to keep the soil heavily saturated, you want to keep it evenly moist and not let it dry out too much in between waterings. This is especially true of tomatoes in containers as uneven watering can contribute to blossom end rot. If your plants are cycling from dry to moist and back to dry again, the plants may not feel like they're receiving consistent enough moisture to carry fruit.

    With regards to the varieties you listed, Brandywine is late, late, late and produces poorly in our heat. Arkansas Traveler is a late one and usually doesn't bloom for me until sometimes in June, and then those fruit are ready to pick by August. Black Krim and Cherokee Purple usually flower for me in late May, but this year they aren't, so I think it is the weather because they're certainly large enough, have consistent moisture and are in well-amended soil with good fertility. Some years Roma can sit and wait forever before it blooms, but once it does, it sets a lot of fruit and they are ready fairly quickly.

    Black Cherry sometimes is slow to start flowerings and setting fruit, and sometimes not. Sometimes it slows down more in the heat of the summer than other cherries do and sometimes it doesn't. It is kind of a garden diva at times, but it gets away with it simply because the flavor of the fruit is so good.

    I don't know what your temperature and humidity have been like for the last two or three weeks, but mine have been too hot on some days for fertilization to occur but not on others. Remember that I said that plants are individuals? I have right around 100 tomato plants and some have already produced several ripe tomatoes, some of which have been quite large, and others haven't even bloomed yet while a few have set and ripened a lot of smallish tomatoes. That is pretty typical behavior.

    Also, tomatoes in containers do not peform exactly like those in the ground. Remember that tomato plants in the ground can send their roots out searching for more water or more nutrition if they need it, but plants in containers are trapped in the containers so cannot help themselves in that same manner. So, tomato plants in containers have a smaller margin of error than those in the ground and they may stunt or stall if they are not happy.

    Some years I have as many as 40 tomato plants in containers. This year I have 9. Why? Because I was expecting a hotter-than-average and drier-than-average growing season and I knew that tomatoes in containers would struggle more in those conditions. Thus I put fewer of them in containers, and my smallest containers this year are 20-gallon containers. I have grown tomatoes in containers as small as 5 gallons, but tomato plants in containers that small are hard to keep happy and often do not produce well in our climate. For maximum production, they need larger containers that hold more moisture, that allow their roots to spread out and that keep their roots cool. Don't overlook the possiblity that the heat is just baking the roots of the plants in containers.


  • 13 years ago
    last modified: 9 years ago


    Thanks, as always, for the well thought out response. The fish emulsion I've been using is indeed 5-1-1. I just assumed that it could be lack of P-K that is keeping them from flowering.

    The issue I'm seeing is mostly no flowers at all. I am seeing SOME blossom drop, but that's only on a few plants, and those plants are also setting fruit.

    Your explanation regarding the varieties I planted is probably a sound one. I went searching after I read your post, and it seems that most of the varieties that aren't blooming are, indeed, "late" varieties. This is only my second year growing anything, so I've got a lot to learn.

    I'm most disappointed that I'm not seeing anything from my 4 black cherry plants. I understand why now, however. I am DYING to try them; I've never had one. From what I've read, it's the "non-tomato person" tomato.

    I'm growing almost everything in containers due to lack of space, so I'm going to have to keep a close eye on them to make sure they're not just cooking. It's been so bloody hot.

    Thanks again, Dawn. I'll snap some pics, too, to post back.

  • 13 years ago
    last modified: 9 years ago

    Mark, You're welcome.

    I understand about the need to grow in containers. There are ways to help keep them cool. Some gardeners buy that foam insulation board that is either white or shiny silver and put 'boxes' (I assume just insulation tacked together with nails or something) around a row of containers to deflect the sunlight away from the pots. Others line up hay bales alongside the pots so the hay bales block the sun. Also, if you have dark color pots, they'll absorb heat, so I am slowly changing to light-colored pots, or painting my dark pots a lighter color with Fusion spray paint for plastics.

    I've also moved my containers off the concrete and onto grass. I like having them on the concrete early in the season when the heat is beneficial, but have to move them in May or they start roasting in the sun.

    Hang in there. I am betting they'll start flowering soon. I have seven Black Cherry tomato plants, and two are flowering and setting fruit just fine. Of those two, one has ripened fruit already. The other five Black Cherry plants are just sitting there like bumps on a log! I guess they'll flower and fruit when they are ready, and not before. All seven are planted in the same row, side by side, so they are a great example of how different plants of the same variety can behave differently even when they all sit there side by side in the same soil, same light, same moisture, etc.

    When I want to manipulate my tomatoes into blooming during a cool spell in the summer so that, hopefully, I'll get fruit set specifically during that cool day or two, I feed them Super Bloom or the Miracle Grow Bloom Booster formula. You might try that on your Black Cherries. If it doesn't make them bloom, then we have to accept that they are at that difficult "stubborn teenager" stage and aren't going to bloom until they make up their mind to do so.


  • 8 years ago

    Dawn (or others) -

    Of my 7 tomato plants, 5 have either 1 or 2 flowers, and the other 2 have none at all.

    I was using a Miracle Grow product that I just noticed is a 24-8-16 formula, so they're probably not getting nearly enough phosphorus (I'm guessing?)

    Is there a product that will introduce more phos. without raising the levels of what they're probably getting too much of with the Miracle Grow product?

  • 8 years ago
    last modified: 8 years ago

    Too much nitrogen is sort of hard to offset, so I am not sure what you could do to get the plants a quick shot of phosphorus. Maybe one of the liquid bone meal products, like the one I've linked below might do it.

    DTE Liquid Bone Meal

    Are you here in Oklahoma? If so, the current hot temperatures both day and night are high enough to impede fruit set in most parts of the state, so even if you get flowers now, assuming you are in OK, they are likely to drop off the plants without setting fruit. Most tomato varieties do not set fruit well once the daytime highs are exceeding 92-95 degrees and the nighttime lows are exceeding 72-75 degrees. The heat causes the pollen to stick together in clumps, which often prevents pollination and fertilization from occurring. Tomatoes are self-pollinating, but in order for the process to work, the pollen needs to be able to move around within the flower which has both female and male parts to make pollination possible. High humidity in addition to high heat just makes the problem even worse. There are a few tomato varieties that are able to set fruit in high heat, and luckily for us, most vareities that set bite-sized fruit also continue to set fruit despite pretty high temperatures.

    With regards to the phosphorus, it doesn't matter how much phosphorus the plants are getting if high temperatures/high humidity are impeding fruit set. However, since your plant are not forming many flowers, excess nitrogen in combination with not enough phosphorus probably is the reason.

    If you are somewhere else, in a lovely, cool mild state where it isn't already hotter than, well, you know where, then maybe the lack of phosphorus can be corrected in time to get blooms and fruit set before hot weather arrives.

    You also could just feed your tomato plants a Bloom Booster fertilizer. Two that I've used in the past are Super Bloom and Miracle Grow Bloom Booster. If they push your plants to flower, and you get lots more flowers but still don't get fruit set, then the issue likely is the combination of high heat/high humidity. To be honest, even when using Miracle Grow, Miracle Grow for Tomatoes or Miracle Grow Bloom Booster, I've never had tomato plants not bloom, so I don't think a lot of nitrogen hurts them as much as we gardeners tend to think it does. I used those fertilizers a lot in our early years here when our soil was not yet well-improved and got tons of tomatoes, even though I could tell from the appearance of the foliage (which was a deep bluish-green) that the plants were, technically speaking, getting too much nitrogen. Since they did set fruit, I didn't worry overly much about the excess nitrogen at that point.

    Once you get flowers, one way you can help the flowers pollinate and fertilize in high heat/high humidity is to thump the flowers, gently shake the cages, or use a hand-held battery-operated toothbrush to buzz the flowers, similar to the way a bee can help pollination by shaking the plant enough to loosen up clumping pollen. Sometimes these methods work in assisting pollination when temperatures are right at the borderline between being just right and too hot.

    Another thing you can do it to watch your 5-day or 7-day forecast for any summer cool fronts that might drop temperatures down low enough for a couple of days to allow fruitset. To ensure your tomato plants are in bloom when that cool front arrives, feed the plants with a Bloom Booster type fertilizer as soon as you see the cool weather in the forecast. This will push the plants to put out some new flowers, hopefully just in time for the cool weather to arrive.

    In Oklahoma, we often go from weather that is too cold to plant tomato plants to temperatures that are too hot for fruit set in a shockingly brief time frame. In order to give our plants the best chance of setting fruit before the high temperatures arrive, it is imperative to plant as early as possible. I try to get my plants in the ground in mid- to late-March, even if it means covering them up with frost blanket row covers on cold night so they won't freeze. Usually I stagger the transplanting of tomato plants over several weeks time from mid-March to mid-April. Any plants I get in the ground later than mid-April probably won't have time to set much fruit before the hot weather arrives, so strive to avoid planting too late. Sometimes we can plant exactly on time and the weather gets hot extra-early and we don't get good fruitset, and there's not much we can do in a year like that. The last year that was really intensely hot early was 2011, and let's hope we never have another year like it. I remember that the temperatures were hitting the 90s during Easter week when I was trying to put tomato plants in the ground while simultaneously thinking it already was too late to get good fruit set. Sometimes we just can't win.

    Be sure you are not overfeeding your plants any single ingredient because, often, an excessive amount of one nutrient can impede the plants' ability to take up and use other nutrients. So can a pH that is much higher or much lower than the pH preferred by tomato plants.

    Sometimes it is a mystery why tomato plants don't flower and set fruit when we expect them to, but often it is something simple that just needs to be corrected---for example, late varieties of tomatoes might not be blooming much yet, depending on where you live. Part of being a gardener involves being a plant detective and studying the case in front of you and figuring out what's going on. Good luck,