Grow · field guide
Blossom End Rot: Why It Happens and How to Stop It
You wait weeks for the first tomato, and the bottom is a sunken brown leathery patch. That is blossom end rot, and the good news is it is not a disease, not a bug, and it does not spread. The cause is almost always how the plant is watered, which means you can fix it.
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What blossom end rot looks like
It starts as a small water-soaked spot on the blossom end (the bottom) of the fruit, then grows into a sunken, dark, leathery patch. It hits tomatoes most, but also peppers, squash, and eggplant. It is a disorder, not an infection, so it will not jump from fruit to fruit.
The real cause is uneven water
Blossom end rot is a calcium problem, but usually not because the soil lacks calcium. It is because swings between bone-dry and soaking-wet soil stop the plant from moving calcium into the fruit. The fix is steady moisture, not more fertilizer.
How to stop it
Keep the water even and the problem usually clears on its own:
- Water deeply and on a schedule, about 1 inch a week, so the soil never swings from dry to flooded.
- Mulch 2 to 3 inches deep to hold moisture steady between waterings.
- A drip line on a timer makes consistent watering almost automatic.
- Go easy on high-nitrogen fertilizer, which pushes fast growth the plant cannot supply with calcium.
What not to waste time on
Tossing eggshells or dumping calcium in the hole rarely helps, because the soil usually has enough calcium already; the plant just cannot move it in dry, swingy conditions. Fix the watering first. The early fruits may be lost, but later ones come in clean once moisture is steady.
Questions, answered straight
Uneven watering. When soil swings between dry and wet, the plant cannot move calcium into the fruit, and the blossom end rots. It is a moisture problem, not usually a soil calcium shortage.
No. It is a disorder, not a disease, so it does not spread. Fix the watering and later fruit comes in healthy, even on the same plant.
Rarely. Most soil already has enough calcium; the problem is the plant cannot take it up in uneven moisture. Steady watering and mulch fix it far more reliably.
Yes. Cut off the bad bottom and the rest of the fruit is fine to eat. It is a physical disorder, not a contamination.
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