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San Marzano Plum Tomatoes

I've been growing the San Marzano variety of plum tomato for many years and have nearly always had the same problem. The inside of the fruits often turn black with what looks like a mold of some sort. Eventually, the whole bottom of the tomato turns black. I can out the bad part, but it's a nuisance when trying to process a lot of tomatoes. Many are so bad that I just throw away the whole tomato. I don't have the same problem with other varieties such as Roma or Debarao.

Does anyone know if there's anything I can do to prevent the problem, or should I just give up on San Marzanos? Not all of the fruits are affected, but I'd guess it's about 50%. I'm wondering whether it's from too much or too little water or perhaps humidity-related. I'm reluctant to use fungicides; I'd rather just grow a variety that doesn't require their use.

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    1. re: yellowstone

      agree. It's definitely BER.

      I also grow San Marzano tomatoes and have had such issues in the past. The best way I corrected my problem was mixing in a little epsom salts into the soil a few weeks before transplanting and hooking up soaker hoses for watering, and keeping on a strict watering schedule.
      I haven't had any BER problems since.

      1. re: Novelli

        It's obviously too late for this year to do anything. I was thinking of going to Plant Science Day at the state Agricultural Extension Station on August 1 and bringing along along a sample of an affected tomato. If they confirm your advice, you're a certified genius, IMO. What do you mean by "a little" epson salts? Are you talking about something like a tablespoon per plant, a cup per plant, or what? This is really hurting because the plants are totally LOADED with fruit this year. So far, at least 50% are bad. Debarao, one of the other varieties I planted, seems to be completely immune to the problem. It's a plum type tomato, but it's not as dry as the San Marzano. Actually, it's more like a cross between a salad and a plum tomato with excellent flavor and productivity. I was ready to give up forever on San Marzamos.

        1. re: stukin

          Never too late.

          BER usually means there is either a lack of calcium in the soil, or your plant is unable to utilize the calcium in the soil. The magnesium found in epsom salts helps this a bit by allowing the plant to suck up the calcium.

          I've read of people actually grinding up some Tums or Rolaids, sprinkling around the plants, and then watering it in to provide the extra calcium boost (same with crushed egg shells). But without knowing your soil structure, it's hard to comment on wether you actually need the calcium or if your plant is having difficulties absorbing it through the root system.

          The best I can tell you for next year is till in some garden lime, toss in a tablespoon of epsom in the hole at the time of planting, and keep the plants on a strict and even watering schedule.

          I would still go to the Plant Science Day and ask around for info. They may be able to better illustrate the issue and it's resolution.

          On a side note, here's a website with interesting info regarding BER and epsom salts.


          Best of luck!

          1. re: Novelli

            It seems strange that the San Marzanos are the only tomatoes that I'm having a problem with. I have 108 plants of 13 different varieties, and they're all planted in the same type of soil. I move them around each year and alternate with other veggies for no particular reason. It also seems strange that some of the tomatoes are perfect while others on the same plant, and even in the same cluster, are affected. Maybe I should be happy that not all of my tomatoes will be edible... I live alone and share them with just one other person. 108 plants does seem a bit absurd when I think about it. The squirrels and chipmunks are fat and happy, and there's still plenty for me.

            1. re: stukin

              I hear ya. It's all trial and error. Learn new things each year.

              Do you have a forest type area near your home/garden? Very hot temperatures?
              If you want to keep the squirrels and chipmunks from sampling your tomatoes, you could set out a couple of containers of water for them to drink instead and usually they'll leave the plants alone. In these hot temperatures lately, their probably looking for something to quench their thirst.

              Rubber snakes (or a cut up old hose) placed around the garden will make them think twice about entering. Just be sure to move them around every couple days so they're not always in the same spots.

              1. re: Novelli

                Brilliant idea! I never had a problem with squirrels until about maybe 15-20 years ago. We had an unusually long drought with some hot temps. That was the first time I ever had any squirrels problems. At first I thought is was racoons, so I trapped and removed several of them. It wasn't until a few months later that I saw a squirrel eating a tomato while sitting on a stump near the garden. Ever since then, the squirrels have come back each year. I knew intuitively that they were after moisture, but it never occurred to me to put out water. What I've done instead has been to just plant more and more tomatoes in the hope that the squirrels would eventually reach their full capacity. They'd usually wipe out all the tomatoes on the plants, but they'd leave the late fruit alone. I guess they weren't smart enough to figure out that plants will keep producing even after the tomatoes are picked clean. I like the idea of water. Gonna try it right now. Where can I buy some snakes?

                1. re: stukin

                  Maybe try the toy section of a Walmart or Target? I've even seen them in the 99 cent type stores. Very cheap.

                  1. re: Novelli

                    I meant alive. A few Burmese pythons would do the trick. Little ones. Twelve feet or so.

                    1. re: stukin

                      Love your spunk, stukin! We, however, tried the fake snake thing, along with the fake owl thing. Our problem was rabbits eating the tomatoes (and of course, one bite out of 12 tomatoes rather than eating 2-3 whole tomatoes). Then we saw one enterprising rabbit standing ON TOP of the fake owl, eating away at a tomato. Maybe the Burmese pythons would work better! Ain't gardening fun?

                      1. re: pine time

                        Your rabbits are much smarter than mine. My big problem is with squirrels and chipmunks. I never saw a rabbit climbing anything. If you use tomato cages, try placing a low fence of chicken wire around the cage. You could also do the same with plants that are staked. I've found that to be highly effective at keeping rabbits at bay, but it won't do any good against woodchucks, squirrels, chipmunks and other climbing critters. My other weapon is a pair of pit bulls that love to kill animals. Their favorite prey is rabbits.

            2. re: Novelli

              At Plant Science Day, I was told that magnesium and calcium counteract each other. The magnesium acidifies while the calcium neutralizes. Regardless, I did the epsom salts thing this year in a totally new location. I also added some lime; the soil was VERY acidic. We've had plenty of rain, plus the plants are well mulched to hold in the moisture. I used a 2-pound bag of epsom salts for 12 plants. There are already several small tomatoes, and I just pulled off one that has BER. With over 150 tomato plants of 13 different varieties, I guess I'll have enough even if I don't get any San Marzano tomatoes. BTW, I highly recommend the Hortonova 13FG Vertical Trellis for growing tomatoes and any other climbing crops. Also, the tomato trellis clips are fantastic. Both are sold by Johnny's Selected Seeds (Johnnyseeds.com or 1-877-564-6697). I'm using them in combination this year for the first time, and I'm extremely impressed.

          2. re: Novelli

            I use one teaspoon of Epsom salts per plant (actually sprinkled over the area where each plant will be) and have no blossom end rot. Each plant area also gets one handful of slow release 10-10-10 ferilizer. I used to add a handful of powdered limestone each year but I figure there's enough in the soil now and have skipped it for a few years.

            1. re: therealdoctorlew

              Mom used Epsom salts on her tomatoes--I had forgotten about it entirely. I have a 5# bag from some cockamamie recipe for Epsom salt-based hair conditioner which didn't work--I'll try it next spring on the 'maters. Thanks.

              1. re: pine time

                Now that the growing season is over, I can see what did well and what didn't. The San Marzano tomatoes were almost free of BER this year for the first time ever. I can opnly attribute that to the epson salt I used in the soil. For the first time ever, my peppers were almost totally free of pepper maggots. I did one spraying early in the season when the first peppers were still tiny, and that seems to have wiped out the flies that do the damage. Next year, instead of spraying my couve (Portuguese kale) to keep the cabbage butterflies at bay, I'm going to use spun fabric row cover. I used it on some of the crop this year, but I didn't have enough to cover it all. The difference was dramatic and without spraying. I enlarged the whole garden by almost 100% to about 3000 square feet, so I should have enough produce to keep me busy and well fed. I put up a deer fence around the whole yard, so hopefully that problem is solved.

                1. re: stukin

                  Congrats on solving your BER problem!! You mentioned peppers in your post, so I figured I'd pass along a tip from one of the chili pepper forums I read earlier in the spring, which I also applied to my regular bell peppers and had great success. In addition to adding Epsom salt to the soil before planting, this guy suggested taking a book of matches, fanning them out and then sticking them into the dirt underneath the plant (or you can use sulfur, but I had a box of matchbooks so I used 'em). They grew like CRAZY!! Also, learned a huge lesson about tomato plants this summer - always cage the indeterminate ones, not stake - I woke up the other day to find half of the plants had fallen over and the main stems snapped. Uggh. Oh well. Trying to ripen all the green ones on the windowsill!!

                  1. re: Savgirl

                    The sulfur in match heads acidifies the soil, and that's what peppers like. Never lime soil where you plan to plant peppers or potatoes. I saw the match trick on TV many years ago on Square Foot Gardening. Epson salt also acidifies the soil, but be careful not to overdo it. If a little is good, more is not necessarily better. I've caged my tomatoes for about 40 years, mostly because I'm extremely lazy. You'll get bigger tomatoes if they're staked, but cages allow you to have more plants in a given area. I just bought a 250X10-foot roll of spun fabric row cover to protect my cole crops (broccoli, kale, couve, etc.) from the cabbage butterflies. I'm trying to avoid spraying as much as possible. I may also try it to stop the squash vine borers from destroying the zucchinis. Butternut squash is the only squash I know of that doesn't seem to be bothered by the borers. My crop wasn't great this year, but last year I got over 400 pounds. If you pick immature butternut squash during the summer, they make an excellent substitute for zucchini. No need to peel or remove the seeds; just slice and grill. The seeds and skin are tender enough to eat the whole thing.

                    1. re: Savgirl

                      Instead of trying to ripen the green tomatoes, make dills pickles out of them! An Italian neighbor taught me to use the end of season green tomatoes that usually ended up being killed by an early frost. Use your favorite dill pickle recipe and quarter them before placing in the jar. They are great used with a Bloody Mary or just in your glass of tomato juice. My family eats them like they would regular dills.

          3. Here's a link to an excellent, helpful video http://www.youtube.com/watch?v=H5QrW0...

            What you have is called "blossom end rot" and is a really common problem with tomatoes. I followed this guy's advice and my tomatoes are doing awesome for the first time, ever!! Adding agricultural gypsum (available at good nurseries or online from Amazon - inexpensive AND it's organic) to the soil when transplanting is crucial to preventing it. Watch his video for the ratio of gypsum to soil. Good luck!!

            3 Replies
            1. re: Savgirl

              Lots of good advice there, but for the number of tomato plants I have - about 200 this year - it would cost me a bloody fortune! I did the lime thing for calcium plus I used some epson salt around the San Marzanos. I've been told for many years that BER is the result of a magnesium deficiency. It's cheap... 88 cents for 2 pounds at Wal-Mart.

              1. re: stukin

                Yikes - that WOULD cost a fortune!! I'm trying straw bale gardening for the first time this season and it's working incredibly well - can't believe how great everything is growing (and I'm a novice gardener - pretty proud of myself right now!). I bought the Joel Karstens book on the method and it's so easy, even I can do it. :-)

                1. re: Savgirl

                  Many years ago, I used the "leaf method." In the fall, I piled all my leaves in the garden up to a depth of at least 4 feet. By the next spring, they had settled down to a depth of about a foot. To plant, I just made openings in the leaves and then pulled them back in around the plants. As the leaves decomposed, they created a constant supply of nutrients. The worms had a wonderful time, there were absolutely no weeds, and I never had to water. That was, by far, the best garden I've ever had. The best I can do now is to save the straw from the big clumps of ornamental grass that I cut down in the fall. I use it as a mulch to hold down the weeds and retain soil moisture. The straw also allows me to grow some tomatoes without supports by keeping them out of contact with the soil.