There’s nothing like putting your heart and soul, sweat, and tears into creating a beautiful vegetable garden only to have your fruits turn out all wrong. Over the coming weeks, I’ll be writing about some reasons your vegetables might not shape up to be county-fair contestants this year. Blossom-end rot is the first early season roadblock most people encounter.

Blossom-end rot occurs in tomatoes, peppers, zucchini, and other cucurbits. Early in the season as fruits develop quickly, they require a lot of calcium. Moisture plays a crucial role in calcium uptake in the plant. Though it may look like disease or insect injury, blossom-end rot is a physiological disorder caused by a lack of calcium transferring from the soil to developing fruits during dry weather.

When a dry spell follows a time when plants get adequate moisture, calcium uptake into tomato plants is interrupted, causing the blossom-end of some fruits to develop a water-soaked, rotten appearance. Symptoms in peppers and cucurbits are similar in appearance, and occur for the same reason. Other factors that contribute to blossom-end rot include overly deep cultivation that damages plant roots and excessive applications of fertilizer containing ammonia and/or salts.

Growing vegetables in containers can be particularly tricky because containers tend to dry out quickly, leading to more extreme fluctuations in soil moisture than what plants experience in the ground. Be sure to water your container plants on a consistent schedule, and apply a fertilizer specifically formulated for tomatoes or vegetables that contains calcium as a micronutrient.

Blossom-end rot is typically an early season garden problem that balances itself out as summer progresses. Here are steps for minimizing blossom-end rot:

• Maintain even soil moisture by adhering to a regular irrigation schedule. Consider mulching around plants to minimize moisture loss.
• Avoid cultivating the soil too deeply and too close to the root systems of vegetable plants.
• Use a fertilizer high in superphosphate and low in nitrogen. When adding nitrogen, use calcium nitrate rather than ammonia or urea forms.
• Have your soil pH tested. Your vegetable garden should have a pH between 6.5 and 7. Visit our website for soil testing instructions.
• As a last resort, use a foliar spray of calcium chloride. Be aware that calcium chloride can be phytotoxic if applied too frequently or in excessive amounts.

Sandra Vultgaggio is Horticulture Consultant for CCE Suffolk. She can be reached at sib7@cornell.edu or 631-727-7850 x387.