top of page

Helping prevent blossom end rot

Steps you can take in the fall to mitigate a common spring issue with fruiting vegetables.

Each spring, we hear from local tomato growers who are finding dark, sunken black or brown patches on the blossom ends of their tomatoes (the side facing away from the stem). Since the tomato plants themselves often seem green, healthy, and actively growing, these customers are understandably confused about why their fruit looks so unhealthy. So in this post, we'll discuss what blossom end rot is and what you can do to help prevent it from claiming your prize tomatoes.

What is blossom end rot?

Blossom end rot (BER) is a frustrating physiological disorder that affects several different fruiting vegetables--tomatoes, eggplants, and peppers in particular. It's caused by calcium deficiency. Over time, calcium-starved tissue breaks down and rots at the "blossom end" of the fruit, often ruining the produce of an otherwise healthy plant.

What makes the disorder so frustrating is that there aren't really any warning signs from the plant to let you know that there's a problem. Since the plant looks green and healthy leading up to the spring, it can feel like the rotting fruit just shows up out of nowhere. This frequently leads customers to suspect disease or pests are the cause instead of soil conditions or root problems.

In order for fruiting vegetables to produce good fruit, a consistent supply of calcium must be both available in the soil and well used by the plant's root system. Root damage, drought stress, extreme fluctuations in soil moisture, or unusually high concentrations of ammonium (common in high-clay soil structures) are all contributors to poor calcium uptake.

Preventative measures

Unfortunately, once you begin observing BER in your fruit, there is little that can be done about the problem--at least until the following season. That's why it's important for gardeners to take steps in the fall to prevent BER before it starts. Here are some suggestions:

  • Improve your soil structure. Especially if you've experienced problems with BER in the past, it's a good idea to take certain steps to build out a more hospitable soil environment for your new tomato plants and fruiting vegetable transplants. In particular, we recommend working in some fresh compost and adding calcium nitrate. Other calcium supplements (garden lime or liquid calcium sprays, for instance) primarily supply calcium to the plant's leaves. Calcium nitrate, however, is absorbed by the roots in a manner that enables calcium to reach the fruit.

  • Establish consistent watering practices. Consistent, proper watering is super important for plants of all kinds, but especially so for sensitive fruiting vegetables like tomatoes, eggplants, and bell peppers. Soil moisture is what enables root systems to take in vital nutrients--including calcium--and push those nutrients all the way out to the fruit. Be sure to revisit our guide to proper watering practices to make sure you're doing it right.

  • Use mulch. Many gardeners overlook the benefits of mulch in their vegetable gardens. Applying about two to three inches creates an insulating layer that helps regulate soil temperature and moisture, giving you more mileage for your watering. Mulch also enriches the soil structure as it breaks down over time. Just be sure to keep it about two inches away from plant stems for better disease control.

Take these precautions now, and your chances of developing BER this spring will be greatly reduced. Of course, we're always eager to help in any way we can. We'll be glad to point you toward just the right products to get your vegetable garden off to the right start. Call or stop by anytime!


bottom of page