What's wrong with my tomato plants?

Amy (7b/8a) NC
June 27, 2019
last modified: June 27, 2019

The leaves and stems are turning yellow at the bottom of the plant. All of my other plants look perfectly healthy except these two (sungold and beef steak). They aren't planted next to each other. Any ideas?

Comments (20)

  • donna_in_sask

    Could be a lot of things. The oldest leaves sometimes turn yellow...or it could be early blight (I remove any yellow/damaged leaves as the season progresses). I noticed the wood chip mulch and have read about it tying up nitrogen to the plant as it breaks down.

  • edweather USDA 9a, HZ 9, Sunset 28

    Definitely get rid of the yellow/problem foliage. Could be several things, but start spraying with a fungicide like Daconil. Foliage near or touching the ground is asking for problems.

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  • lgteacher

    Remove the yellow leaves - probably fungus. Also, pull the wood chips back a little from around the main stem so the stems are not too wet.

  • kevin9408

    Amy, without a doubt your tomato plants have a Macro nutrient deficiency. I magnified your pictures and saw no black or brown spots or rings developing on the lower leaves as a sign of fungus. Spots would start to appear on green leaves if it were early blight or septoria leaf spot, the two most common fungus effecting tomatoes found in most soil.

    The nutrient you're in need of is potassium or nitrogen just by seeing the tomatoes on the plant. Potassium is mobile in the plant and will move out of the lower leaves to support the high demand for potassium in newer leaves and fruit growth. Nitrogen deficiency is also a possibility and is also mobile in the plant.

    I suggest you amend the soil with soluble potassium and nitrogen to stop the problem and it will also give you bigger and better tomatoes. A banana peel or organic source will take weeks to breakdown by bacteria to supply the nutrients the plant can take up so I will suggest potassium nitrate as the quickest fix there is. It is water soluble and is 15% nitrogen and 46% potassium in it. When tomato plants start producing fruit the demand for potassium triples and this is the perfect ratio for tomatoes in the fruit bulking stage. Potassium nitrate also known as salt peter is expensive and hard to find. But very little is needed, about a 3 or 4 grams or a half to full teaspoon per plant depending on plant size.

    You can find Potassium nitrate at any home and garden store but you must find or ask for "stump remover". Don't let the name scare you, it is 100% potassium nitrate and will say that on the ingredient label. Price is about $7 to $8 for 1 lb. Other online sources will sell you greenhouse grade potassium nitrate for a buck or two a pound. There is no difference between the two, both 100% potassium nitrate.

    Amy (7b/8a) NC thanked kevin9408
  • SW (Sydney, USDA 10b)

    Agree with a Kevin that there’s no sign of disease.

  • daninthedirt (USDA 8a, HZ10, Cent TX, Sunset z30)

    Kind of strange that two plants have a nutrient deficiency, but others don't. Brown and yellow lower leaves almost touching the soil says fungus to me. As noted, I'd get out the Daconil and start treating. Those infected leaves won't get any better, but unaffected leaves and especially new growth will be fine. Wood chip mulch on top of the soil won't tie up nitrogen. It will if you dig it in. That is, nitrogen gets tied up in the decaying wood chips, not what they're sitting on top of.

  • kevin9408

    Biggest mistake people make with tomatoes is not knowing when to fertilize and how much. This chart shows the dramatic increase in potassium and Nitrogen uptake required as a healthy plant is it grows.

    Very few increase nutrient supply as demand moves into the flowering and fruit bulking stage, so the plant takes nutrients from the bottom leaves and they turn yellow and die. The plant will continue to take nutrients from the leaves, from bottom to top, to provide for the fruit seed even if it means death of the plant, it's all about survival of the seed.

    At some point the weak unhealthy starved leaves will be attacked by a fungus because that is what fungus do. Weak stressed plants are an easy target for fungus even if the seed packet states it is resistant to different fungus.

    People see the bottom leaves turning yellow and the first programed response is to say blight. Unless you see the tell tale signs of a fungus infection, and they're easy to see, why would you spray with fungicide?

    I have healthy plants until the first hard frost because I fertilize right, while others had dead plants a month earlier from what they think was blight. They died from fungus attacking weak unhealthy stressed plants. I do get fungus attacks at times but know how to identity the difference, and at that point I treat them. I alternate with fungicides from 2 different groups of fungicides to insure fungus immune to one group are also controlled.

    I use a copper fungicide (group M1) and chlorothalonil, the same as Daconil , (group M5) and it has been highly effective.

    I see no signs of a fungus on Amy's leaves, I see a nutrient deficiency and after taking another look I still see no signs of fungus.

    Amy (7b/8a) NC thanked kevin9408
  • kevin9408

    Found some fungus growing on a few of my field planted tomato plants today so I took some pictures.

    This is what you'll see if you have early blight of leaf spot.

    I cut off the infected leaves and will spray with a copper spray tomorrow.

    does your leaves have the spots Amy? Didn't see any.

    I couldn't resist taking a picture of a few of my side yard tomato plants. Planted the last week of May, caged with concrete wire and will fed. Pushing 6 ft. tall now.

  • daninthedirt (USDA 8a, HZ10, Cent TX, Sunset z30)

    I think spotted leaves is septoria or spotted wilt. But blights often take out the whole leaf, without spots, much like what I see in Amy's picture. The fact that the lower leaves are affected probably suggests that it isn't verticillium or fusarium. Those start at the top.

    Also, it's pretty obvious that nutrient requirements increase with age. As the plant gets larger, it needs more nutrients. That's true of every plant.

  • tessie83856

    kevin9408, how often do you apply the Potassium nitrate? Dig it into the soil or can you dissolve it in water and give to the plant?

  • kevin9408

    I apply about every two weeks and you can just throw it on top as I do or you can dig it in or mix it with water. They all work fine but I have increased the amount I used from what I posted earlier. My plants are in full bulking stage, massive and full of huge green tomatoes. The demand for potassium is 3 to 4 times what they were a month ago. I'm up to about 3 teaspoons now.

    here is an updated picture taken 3 days ago.

  • tessie83856

    Will the potassium nitrate work on peppers too?

  • daninthedirt (USDA 8a, HZ10, Cent TX, Sunset z30)

    Where potassium works is where the soil is low in potassium. As I said, the fact that you have some plants without the problem strongly suggests it isn't a nutrient deficiency. Serious nutrient deficiencies simply don't happen to one or two plants in a bed and not the others. Adding lots of potassium to soil that already has enough is going to cause other problems. Too much potassium interferes with nutrient absorption of just about everything else. So you can really poison your soil by pretending you have a potassium deficiency if you don't. Unlike nitrogen and phosphorous, potassium is actually not incorporated into plants. It acts as a catalyst for beneficial reactions.

    In the long run, I'd get a soil test done so you know what's going on. That's how you really assess nutrient deficiencies. In the short run, ask a neighbor who has done one. Again, a fungal infection is most likely here.

  • kevin9408

    Not likely a fungal infection and your assessment is wrong.

    Your description: "blights often take out the whole leaf, without spots, much like what I see in Amy's picture. "

    University of Minnesota's description: Signs and symptoms


    • Initially small dark spots form on older foliage near the ground
    • Leaf spots are round, brown and can grow up to half inch in diameter.
    • Larger spots have target like concentric rings and tissue around spots often turns yellow
    • Severely infected leaves turn brown and fall off, or dead, dried leaves may cling to the stem

    The University of Maine's description: Symptoms

    Early blight produces a wide range of symptoms at all stages of plant growth. It can cause damping-off, collar rot, stem cankers, leaf blight, and fruit rot. The classic symptoms occur on the leaves where circular lesions up to 1/2″ in diameter are produced. Within these lesions dark, concentric circles can be seen. The leaf blight phase usually begins on the lower, older leaves and progresses up the plant. Infected leaves eventually wither, die, and fall from the plant.

    I could cut and paste a thousand of these but won't. The point is you are wrong and outnumbered by people much more qualified then you or I.

  • kevin9408

    tessie, potassium nitrate will work great for bell peppers but let me put this in prospective.

    My goal 4 years ago was to find the best way to fertilize for perfect vegetables without contaminating the soil and my water well 80' below in the ground. I also did not want to pay hundreds of dollars a year for required soil sample tests and expensive plant tissue texts throughout the season to determine how much to apply. As far as home gardening is concerned Few do it and even less of those who say "have it tested" do it, cheap talk.

    I determined the only way was "Demand Neutral", a term I made up. It involved finding the data from countless research studies over the last 40 yrs, determine the average amount of nutrients each type of plant actually takes up based on science and only feed what that plant will use during it's life span. The final result is to feed only what plants demand when they need it (and most vegetables differ in demand) , and maintain a net nutrient change in the soil to neutral (take none, leave none). If you go organic none of this matters, but I don't.

    Back to peppers:

    In the first 30 days a pepper plant uptake of potassium and nitrogen is low and slowly grows with every day that goes by, and the amounts of each fertilizer remains equal as a ratio of 1 to 1.

    After about 30 days nitrogen demand peaks, levels off and remains constant for each day that goes by, but potassium demand continues to increase for each day and doesn't peak until about 60 days from planting.

    At this point daily demand for potassium is 3 times what it was at 30 days of age but daily demand for nitrogen has stayed the same as it was at 30 days. So the amount of potassium required is 3 times higher then nitrogen at 60 days compared to the 30 day point. So the ratio of potassium at 60 days compared to nitrogen at 60 days is 3 to 1.

    The Actual nutrient demand for two weeks is what I'll feed them and it will change every two weeks, nothing more or nothing less then proven demand by science. (does not apply to organic gardening).

    There is nothing you can buy that can increase amounts and change ratios to meet demand at different growth stages, nothing. All have constant nutrient ratios you can't change, and instructions state to feed them the same amount through the life of the plant. End result is a lack of one nutrient during fruit production and a excess of other nutrients the plant doesn't need. You'll end up with problems like bad tasting fruit, small fruit, deformed fruit or rotten fruit and also end up dumping excess fertilizer in the soil possibly causing toxicity to your plant of some form and polluting the ground water. The "one size fits all" term does not work when fertilizing veggies, or even lawns. (unless organic)

    The products on the market also contain the wrong forms of fertilizers only for the fact they're cheaper. For example many use potassium chloride which is the cheapest but the chloride in it is slightly toxic to peppers and tomatoes and deadly at higher concentrations.

    There are also problems with the wrong forms of nitrogen where nitrate nitrogen is superior over ammonium nitrogen for peppers and tomatoes. (but of course going organic there is nothing to worry about.)

    So it doesn't matter what you buy, miracle-gow, jobes, all purpose 10-10-10, 5-5-10, 20-20-20 or what ever, at some point you're not feeding enough of one and dumping excess of the others into the ground water. 95% of web sites are misguiding the public and adding to leaching problems. No one addresses this because of the complexity, but again going organic isn't complex, only hard work.

    It is very difficult to give you recommendations at this time because of the complexity involved. I use Potassium nitrate, potassium sulfate, diammonium phosphate, Urea, calcium nitrate, magnesium sulfate, along with all the other micro nutrients throughout the season and the amounts differ every two week based on demand.

    The best thing I can tell you right now is add 1/2 to 1 teaspoons potassium nitrate per plant every two weeks for healthier plants, and better tasting peppers. This equals to less then 1 gram - 2 grams by total weight of potassium and also equals about the same potassium you'd get from a banana peel. Why not use a peel? they take several weeks to break down for the available potassium plants can use.

  • daninthedirt (USDA 8a, HZ10, Cent TX, Sunset z30)

    My fungal infections don't have spots. But septoria certainly does. I said they OFTEN don't have spots. You missed that word. Read carefully.

    You have zero evidence for nutrient deficiency here, but you insist on it as a cause. I have tomatoes that look like that, and I have no such nutrient deficiency, according to soil tests.

    Fertilization to fix nutrient deficiencies that don't exist are often the cause of new problems.

    You do NOT pay "hundreds of dollars a year for required soil sample tests". That's just blatantly false, and new gardeners shouldn't be led to believe that. The OP is in North Carolina, and that state offers very inexpensive tests --   

  • tessie83856

    kevin9408, Thank you for the information. I will give my tomato leaves another good look, but I didn't notice any spots. Most of the plants have some lower yellow leaves, not just a couple. So I am thinking it involves all the tomatoes. As for the peppers, they haven't grown much since I put them in about the first of June. But I have never done very well with peppers. I will put your information in my notebook and read my fertilizer labels. Now I just have to see if I can find stump remover, which should be available in this area.

  • Robin Morris

    kevin9408, this is off topic, but what did you use for that giant cage in the picture you shared? My cages are only 5' tall but my tomatoes are 8' and growing... it is a jungle and my cages are insufficient. I also planted them too close together... live and learn!

  • kevin9408

    Robin, my main cages are made from 5' wide concrete wire shaped like a cone with the fronts held together with high tensile 11 ga. fence wire. The one in the picture has another 4' high welded wire fence section shaped like a cone to match the lower cage and wired on the lower cage with bailing wire. I also cut squares out of the top fence to get my hands in side. It's not very practical and was done in haste with a scrap section of fence. Looks cool but again not practical.

    A future idea is to make something similar to the shape in the picture with supports to ground at the very top region. I guess you could call it a tomato arbor, mainly for cherry tomatoes that I've had well over 10' high (if you stretched out the tangled mess), or my Campari mountain magic tomato plants that produce 200-300 golf size fruit. I think this may work good if the top region leveled off and rolled over at 6 to 7 ft. high, and the plant growth stayed above the cage but the tomato clusters hung through and below the cage. If the vines made it to the outer region they could weep over and down, with 2 to 4 plants grown together in the center and pruned hard until they got up to the red section, what do you think? Or maybe a half or quarter circle training one plant up?

  • Robin Morris

    kevin9408, I love the idea of a tomato arbor... I was thinking of something similar. Have you come up with a way to build it? I think it that shape would work, but would be a lot of work to support it.

    I posted on here a while back asking for ideas for some attractive extra large tomato solutions as my tomatoes are in my front yard. I find any ideas I loved in time, so I stuck with my 5' concrete wire cages (they are ugly, but invisible this time of year). All my tomatoes except for 2 are a good 2-3' above the cages this year... I think I went a bit too heavy with the nitrogen in May.

    I made the mistake of planting a sungold on either side of a path and they naturally formed an arbor over it although there is only a 4' high path under it, so now I am crouching to pick them.

    It would be a bit $$, but I was thinking about getting a bunch of these for next year:

    and place the tomatoes and my 5' cages on each side of the arbor with a slight tilt toward the arbor... Then I would grow the tomatoes over the arch and have a tomato pathway in my front yard. That should give them enough space (although I once had a sweet 100 grow 14' up to my roof).

    Anyway, sorry to hijack the thread OP. I hope your tomatoes recover.

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