Garden Troubleshooting: Blossom End Rot

What is blossom end rot?

Blossom end rot is a physiological disorder, which means it is not caused by a germ or an insect. It shows as a tan, brown or black leathery patch at the blossom end of tomatoes, peppers, squash and sometimes melons, the end opposite the stem.

It tends to hit the first fruit of the season hardest and may fade later. The affected fruit is not spreading an infection to the rest of the plant, though mold may grow on the damaged area.

Squash and pepper plants can show it too, and in squash the rotted end can look like decay after a rainy spell. Because the damage looks like a rot, many gardeners assume a disease and reach for sprays that do nothing. Recognizing it as a growing problem saves money and effort.

• Starts as a small water-soaked spot
• Enlarges and turns dark and sunken
• Seen on the earliest fruit most often

Does it mean my soil lacks calcium?

Not necessarily. The problem is a shortage of calcium in the developing fruit, but many soils contain plenty. Calcium moves through the plant with water, so anything that interrupts steady water uptake can leave fruit short even in rich soil.

That is why extension sources point first to watering. Adding calcium products without a soil test often does little, and heavy nitrogen or some other nutrient imbalances can make matters worse.

Another point worth knowing is that root health affects calcium uptake. Roots damaged by tools, heavy rain, pests or compacted soil take up less water and less calcium. Planting into loose, well-prepared soil and avoiding root injury during hoeing gives plants the best chance of getting what they need.

• Test soil before adding any amendment
• Follow label directions on anything you use
• Do not assume the soil is deficient

How does watering cause it?

Swings between dry and wet soil are the main trigger. A dry spell slows calcium movement just as fruit is growing, and a big rain or heavy watering afterward pushes growth fast. Hot, windy days make plants lose water quickly and compound the problem.

Aim for evenly moist soil. Deep watering once or twice a week in most conditions beats daily sprinkles, though sandy soils and containers dry faster and need closer attention.

• Use a drip line or soaker at the base
• Water on a steady schedule
• Check moisture with your finger, not by guessing

What can I do right now?

Pick off the affected fruit so the plant puts energy into healthy ones. Then check moisture and mulch the bed with straw, leaves or similar material to hold water evenly.

Avoid deep cultivation near plants, since damaged roots take up water less well. Make sure plants are not crowded and that they have enough sun and airflow.

Be realistic about the early fruit. The first tomatoes of the season often grow when plants are still small and the roots are not yet extensive, so the first flush is more likely to show damage. Later fruit usually looks better as the root system grows and the weather settles.

• Remove affected fruit
• Mulch to even out soil moisture
• Do not cultivate close to roots

Does the variety or the bed matter?

Yes. Some tomato types, especially large paste and plum varieties, are more prone to the problem, and containers and sandy soils dry out faster. Raised beds with plenty of organic matter hold water more evenly.

Soil pH also affects nutrient uptake, so a test that shows very low pH may call for correction on a schedule suited to your soil.

• Add organic matter to improve water holding
• Use large containers rather than small ones
• Ask extension which varieties do well locally

How can I prevent it next season?

Prepare the bed early with compost, set up drip or a soaker before planting, and mulch after the soil has warmed. Keep records of rainfall and watering so you can see what preceded the problem.

If it keeps happening despite steady watering and a normal soil test, take a photo and a few fruit to your extension office for a second opinion.

A written watering routine helps more than any single product. Note rainfall, check soil with a finger, and adjust when weather changes. Many gardeners find a rain gauge a handy and inexpensive tool, since it shows how much water plants actually received, rather than how much you think they did.

Last reviewed: November 12, 2026. Written by the Homestead & Small Farm Editorial Team. See our editorial policy.