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Have you experienced blossom end rot before? Blossom end rot is commonly found on tomato, zucchini, pepper, squash, eggplant, and watermelon fruit. It's often mistaken for a disease, but it's actually caused by calcium deficiency in the plant (not always in the soil)! Calcium is a macronutrient required for plant cell walls and cell elongation among other functions. Calcium is taken up passively into plant roots along with water. Deficiency symptoms in leaves are rare so sometimes it is difficult to know if plant calcium is low until blossom end rot appears! Blossom end rot is more common if the growing season begins wet and then shifts to become dry during fruit set. This causes calcium absorption to decrease in the plant as fruit develop. If your growing season is following this trend, practice good irrigation management to increase calcium absorption potential during fruit development.

Calcium is most available in soils with neutral pH (around 7) and becomes less available in slightly acidic (pH of 6) or slightly alkaline (pH of 8) soils. Adjusting your soil pH may help increase calcium availability and reverse the effects of blossom end rot. Options for increasing calcium content of deficient soils include lime (which will increase soil pH), gypsum (which will not change soil pH), or crushed egg shells, oyster/snail shells, or animal bones (bone meal).

Some varieties are prone to blossom end rot while others are resistant to it. Keep good plant records to better understand what crops and varieties show calcium deficiency in which areas of your field or garden.