Blossom end rot
A dark, sunken patch on the bottom of tomatoes and peppers, from uneven watering.
What you'll see
- A water-soaked tan spot on the bottom of young fruit.
- The spot darkens to brown or black, sinks and turns leathery; the first fruits are often hit.
- Affects tomatoes, peppers, eggplant, squash and watermelon.
Why it happens
Fast-growing fruit runs short of calcium because uneven watering stops calcium from reaching it. The soil itself rarely lacks calcium.
How to fix it
- Pick off affected fruit; later fruit can be fine once watering is steady.
- Keep the soil evenly moist: water deeply and regularly, and never let containers dry out.
- Mulch around the plants to hold moisture.
Keep it from coming back
- Grow in large containers or in the ground, where moisture stays steadier.
- In hot spells, water pots twice a day rather than once with double the amount.
- Test the soil, and keep the pH near 6.3 to 7.0.
Read more
- Mulch basics
- How to protect plants in a heat wave
- Growing vegetables in containers
- Watering a vegetable garden
Sources
- Missouri Botanical Garden: Blossom end rot of tomato and pepper
- RHS: Blossom end rot
- University of Maryland Extension: Blossom end rot on vegetables
General guidance, not a diagnosis. For valuable, edible or outdoor crops, check with a local extension service or plant expert. Use any product exactly as its label says, and keep children and pets away while it dries.