Blossom End Rot: Why Tomatoes Get Black Bottom
Blossom end rot is a calcium deficiency caused by inconsistent watering, not lack of calcium in soil. Fix the watering, not the soil.
The black, sunken spot on the bottom of the tomato looks like disease. It’s actually a water issue.
How to Confirm
- Black, sunken spot on the bottom of the fruit
- Spot appears before fruit ripens
- Affects tomatoes, peppers, zucchini
- Not soft or fuzzy (not a disease)
Why It Happens
Calcium moves through the plant via water. If watering is inconsistent — dry spells followed by heavy watering — calcium can’t reach the fruit. The tissue dies.
The cause is not calcium-deficient soil. It’s inconsistent moisture.
How to Fix It
Step 1: Consistent Watering
Water deeply every 2-3 days. Don’t let soil dry out completely.
Step 2: Mulch
2 inches of straw or compost. Keeps moisture consistent.
Step 3: Don’t Over-Fertilize
High nitrogen makes it worse. Skip fertilizer for 2 weeks.
Step 4: Remove Affected Fruit
It won’t recover. Remove so plant puts energy into new fruit.
Step 5: Wait
New fruit should be fine if watering is consistent.
Prevention
- Water consistently (this is 90% of the fix)
- Mulch
- Don’t over-fertilize
- Avoid damaging roots
- Don’t plant in cold soil
Common Questions
Should I add calcium to soil? Usually no. Soil has calcium. It’s a transport issue.
Will affected fruit recover? No. Remove it.
Does this affect other vegetables? Yes. Peppers, zucchini, and eggplant can get it.
Is it a disease? No. It’s a physiological disorder.
Can I eat affected fruit? The unaffected parts, yes. Cut off the black spot.
Will it happen every year? Only if watering stays inconsistent. Fix that and it stops.