Blossom-end rot appears as a small, sunken, tan or dark patch at the end of a pepper opposite the stem. It is not a contagious infection, but it signals that the developing fruit did not receive calcium consistently while its tissues were forming.
Inspect the correct end
Look at the blossom end of young and ripening peppers, especially after a period of fast growth. The first mark may feel slightly leathery before it enlarges and turns dark. Affected tissue can become vulnerable to secondary mold, so avoid judging the original cause from the later fuzzy growth alone. Check several fruits and compare them with healthy peppers on the same plant.
Separate it from other damage
Sunscald usually appears on the exposed side of the fruit as a pale, papery patch, while insect feeding leaves holes or irregular scars. Soft rot may start near a wound or stem and spread rapidly. Blossom-end rot consistently begins at the flower end and often affects fruit during uneven watering or rapid temperature changes.
Improve moisture consistency
Remove badly damaged fruit with clean pruners so the plant can direct energy to new growth. Water deeply when the upper soil begins to dry, then mulch with a thin layer of compost or untreated organic mulch while keeping it away from the stem. Avoid alternating between bone-dry soil and flooding. Container peppers may need more frequent checks because their roots have less soil volume.
Use fertilizer carefully
Do not automatically add calcium without a soil test. Most cases involve uneven water uptake rather than a total lack of calcium in the soil. Avoid heavy nitrogen feeding, which can produce lush foliage and rapid growth. If the soil test shows a deficiency, follow a measured local recommendation and keep watering regular.
Blossom-end rot on one flush does not mean the whole plant is lost. Stable moisture, a healthy root zone, and careful observation usually give later peppers a better chance of developing cleanly.