Q: Last year’s tomatoes were sunken, blackened, and rotten on the bottom end.  What caused that problem, and how can I avoid it this year?

Blossom end rot is a physiological problem that most commonly affects tomatoes, peppers, eggplant, squash and melons.  Its cause is either a lack of available calcium in the soil, most commonly caused by irregular watering.  Annually amending the soil with limestone, preferably in the autumn, can help ensure adequate calcium presence.  Sending a soil sample away for testing can give you a more precise idea of how much lime your garden requires, and will tell you whether it is also magnesium-deficient.  Dolomite lime supplies both calcium and magnesium, while agricultural lime supplies calcium only.

Q: Last year’s tomatoes were sunken, blackened, and rotten on the bottom end.  What caused that problem, and how can I avoid it this year?

Blossom end rot is a physiological problem that most commonly affects tomatoes, peppers, eggplant, squash and melons.  Its cause is either a lack of available calcium in the soil, most commonly caused by irregular watering.  Annually amending the soil with limestone, preferably in the autumn, can help ensure adequate calcium presence.  Sending a soil sample away for testing can give you a more precise idea of how much lime your garden requires, and will tell you whether it is also magnesium-deficient.  Dolomite lime supplies both calcium and magnesium, while agricultural lime supplies calcium only.

Your tomatoes will only be able to access soil calcium if they receive adequate and consistent watering through the summer.  Make sure that your watering method is getting moisture into the root zone to encourage a healthy root system; if you water deeply, you shouldn’t have to water daily except during an extreme heat wave.  Pick a watering regime for your tomatoes and stick to it. If you want to encourage fruit set or fruit ripening by reducing watering, do this as a gradual taper-off instead of cold-turkey deprivation. 

If you do have blossom end rot, don’t despair; keep to a regular watering regime, and later fruiting may be free of the symptoms.  The unaffected parts of fruit with minor rot can be eaten; these usually taste just fine!


Laura Matter, Natural Soil Building Program Manager at The Garden Hotline
The Garden Hotline can be reached at 206-633-0224, Monday through Saturday from 9 a.m. to 5 p.m. Questions can also be emailed to help@gardenhotline.org This e-mail address is being protected from spambots. You need JavaScript enabled to view it .
More information can be found at http://www.gardenhotline.org/

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