Blossom End Rot & Sunscald

 Causes & Differences

🦠 Plant Diseases| by Guy Saldiveri | April 9, 2026

You have a thriving tomato or pepper plant. Leaves vibrant green, stems full of flowers and fruit, everything looking nice and healthy—until you notice that spot. 

It could be on the very bottom of the fruit, or on the side. Similar in appearance—blanched white and spreading outward—it looks like a sore that should be oozing, but it's hard and scaly—at least initially.

You stare, scratch your head, and wonder just what is going on here. You've done everything right, your plants look healthier than they have ever looked, well-watered, well-fed, but this…

There are two possibilities, caused by two very distinct issues.

You are most likely dealing with either Sunscald or Blossom End Rot. Both are very common issues that, believe it or not, are not classified as actual diseases. Both, however, affect just about every gardener that's ever grown these types of vegetables. 

So if they aren't actual diseases, what are they, what are the causes and what are the differences? 

Well, let's start with an easy way to tell them apart. While they look very similar initially, they appear in different locations on the fruit. Sunscald will always show up on the sides of the fruit—the side that is in the direct path of that hot afternoon sun. 

Pepper with Sunscald

Sunscald is actually a burn caused by too much heat. 

The cure for it? Very simple: move the plant or provide a little shade to keep that hot sun from cooking that pepper, tomato, or squash. It really is that simple. And the best part—the fruit is still edible. All you have to do is cut out that bad patch and use the rest just as you would normally do. Sunscald doesn't cause any damage other than what you actually see. 

It's no different from you getting a really bad sunburn. The only real difference is the fruit won't recover from it like you do.

Blossom End Rot (BER) is a bit more serious—and a bit more misunderstood.

It shows up on the bottom (blossom end) of the fruit, starting as a pale spot that darkens into a sunken, brown or black rot.

Pepper with Blossom End Rot

BER is commonly linked to a calcium deficiency—but here’s the key: its cause is usually not due to a lack of calcium in the soil. Most of the time, the real issue is inconsistent moisture levels.

When soil swings between too wet and too dry, fine root hairs are damaged. This disrupts the plant’s ability to move calcium (and other nutrients) up into the developing fruit.

The result? That telltale rot at the bottom.

How to prevent Blossom End Rot

• Keep soil consistently moist—not soggy, not dry

• Water when the top 2–3 inches of soil are dry

• Ensure soil has adequate nutrients 

• Fertilize at planting, then lightly throughout the season

Most in-ground soils already contain sufficient calcium. If you’re unsure, a soil test through your local extension service is inexpensive and incredibly helpful.

For container growing, adding a small amount of pelletized lime at the start of the season can supply enough calcium. Slow-release fertilizers are also a great option, providing steady nutrients over time.

If you’re unsure how to create a good-quality container mix, check out my post on Basic Soil Information and My Go-To Mix. It walks you through everything step-by-step and shows you how to build a low-cost mix that performs well all season.

Once BER appears on a fruit, there’s no saving it. The plant itself is fine—but that fruit is done. Remove it and let the plant focus on producing new, healthy growth.

Both issues are common—both are manageable.

With proper sunlight, consistent watering, and balanced nutrition, you can prevent them entirely.

And if they do show up? Don’t sweat it. Every gardener deals with this at some point. It’s part of the process. The key is knowing what you’re looking at—and how to respond.

Happy Gardening 🌱