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Blossom-End Rot

Blossom-End Rot

Disorderalso: BER

A common and frustrating disorder, not a disease, in which the bottom of the fruit turns into a sunken brown leathery patch. It strikes tomatoes most often, along with peppers, squash, eggplant, and melons, and is usually worst on the first fruit of the season. It comes from a calcium shortage in the fruit, almost always driven by uneven watering rather than by a lack of calcium in the soil.

🔎 How to spot it

Look for a water-soaked spot at the blossom end, the bottom of the fruit opposite the stem, that enlarges into a sunken, flat, dark brown to black leathery patch. It can affect green or ripening fruit and may cover up to half the fruit. Secondary molds sometimes colonize the dead tissue. The rest of the fruit usually looks and tastes normal.

🥀 Damage it causes

Affected fruit is disfigured and unusable, and the loss often hits the earliest and largest fruit hardest. The problem can recur through a flush of fruit until growing conditions even out. It does not spread from plant to plant and does not infect leaves or stems.

🔬 What causes it

Blossom-end rot is a calcium deficiency inside the developing fruit. Because calcium moves with water through the plant, anything that disrupts steady water uptake, swings between wet and dry soil, drought, root damage, heavy nitrogen feeding, or rapid growth in hot weather, can starve the fruit of calcium even when the soil has plenty. Most garden soils already contain enough calcium.

🛡️ Prevent it

Keep soil moisture even and steady, watering deeply and regularly rather than letting plants swing from dry to soaked. Mulch to conserve moisture and buffer the swings. Avoid heavy nitrogen, especially fast-release forms, and do not damage roots when cultivating near the plant. Test the soil and add lime only if it confirms low calcium or low pH. Harden off and plant out so early fruit sets under steadier conditions.

🧯 If it is already here

There is no cure for an affected fruit, so pick and discard the damaged ones to let the plant put energy into new fruit. Then correct the watering, since even, consistent moisture is the real fix. Foliar calcium sprays are widely sold but give little reliable benefit, because fruit takes up very little calcium through its skin. Conditions usually improve on their own as the weather steadies.

💡 Good to know

Blossom-end rot is a symptom of water management, not a soil calcium problem, which is why adding calcium rarely helps. It is most common early in the season and on the first fruit, then tapers off as the root system matures and the weather settles. Container plants are especially prone because their soil dries out fast.

🌱 Plants it affects

102 plants in the library can be affected by this problem

Acorn SquashAji Amarillo PepperAmish Paste TomatoAnaheim PepperArmenian CucumberAtlantic Giant PumpkinBanana Pepper🍅Beefmaster TomatoBetter Boy Tomato🍅Big Beef TomatoBig Boy TomatoBitter MelonBlack Beauty EggplantBlack Beauty ZucchiniBlack Cherry Tomato🍉Black Diamond WatermelonBlack Krim Tomato🥒Boston Pickling Cucumber🍅Box Car Willie TomatoBrandywine TomatoButtercup SquashButternut SquashCarolina Reaper PepperCasaba MelonCayenne PepperCelebrity TomatoCharleston Gray WatermelonCherokee Purple TomatoCinderella PumpkinCostata Romanesco ZucchiniCrenshaw MelonCrimson Sweet WatermelonCubanelle PepperDelicata Squash🥒Diva CucumberEarly Girl Tomato🥒English CucumberFairy Tale EggplantFresno PepperGalia Melon🍅German Queen TomatoGhost PepperGreen Bell PepperGreen Zebra TomatoHabanero PepperHoneydew MelonHubbard SquashHungarian Wax PepperIndigo Rose TomatoItalian EggplantJack-O-Lantern PumpkinJalapeño PepperJapanese Eggplant🍉Jubilee WatermelonJuliet Grape TomatoKabocha SquashKellogg's Breakfast TomatoKirby Cucumber🍅La Roma IV TomatoLemon Boy TomatoLemon CucumberMarketmore Cucumber🍉Mini Love Watermelon🍉Moon and Stars Watermelon🍅Mortgage Lifter TomatoMr. Stripey TomatoOrange Bell Pepper🍉Orangeglo WatermelonPadrón PepperPattypan SquashPersian CucumberPickling CucumberPimento PepperPineapple TomatoPoblano PepperPurple Bell PepperRed Bell PepperRoma Tomato🍆Rosa Bianca Eggplant🍅Rutgers TomatoSan Marzano TomatoScotch Bonnet PepperSerrano PepperShishito PepperSpaghetti Squash🍅Striped German TomatoSugar Baby Watermelon🎃Sugar Pie Pumpkin🍅Sungold Cherry TomatoSuyo Long CucumberSweet 100 Cherry TomatoSweet Banana PepperThai Chili Pepper🍅Tiny Tim Cherry TomatoTrinidad Scorpion PepperTromboncino SquashWinter MelonYellow Bell PepperYellow Crookneck Squash🍉Yellow Doll Watermelon

For educational and informational purposes only. Disease management advice is general guidance drawn from university cooperative extension sources; always identify a problem positively and read and follow the label on any product before use, especially around food crops, children, and pets.