Blossom End Rot

Photo courtesy of PlantNatural.com

Have you ever had brown, leathery spots on the bottom of your tomatoes, cucumbers, or eggplants? It’s likely that was blossom end rot. Let’s talk causes and treatments…

What is blossom end rot?

Blossom end rot is where the bottom (the blossom end, opposite the stem) of the plant’s fruit starts to rot. This can affect most fruiting vegetables, including eggplants, peppers, squash, and tomatoes. The rot starts out looking like an unusual spot or bruising, and later can develop into a larger brown leathery spot that can affect a good portion of the fruit. Though you can cut around these spots and eat the rest, it can seriously reduce your harvest.

What causes blossom end rot?

Though it looks like a disease, blossom end rot is actually a physiological disorder caused by calcium deficiency. Calcium is vital for the development of strong cell walls in plants, and the rotting of blossom end rot means the fruit tissues are lacking in the nutrient. This can either be because there isn’t enough calcium available to the plant in the soil, or (more likely) something is interfering with the plant’s ability to uptake the calcium. Let’s go over the causes of blossom end rot:

• Inconsistent watering.

  • This is the most common cause of blossom end rot. When soil moisture fluctuates too much, it prevents your plant from being able to intake calcium. Plants in containers are the most susceptible to this since containers can dry out so quickly.

• Too much nitrogen heavy fertilizer.

  • In the early season, it’s good to fertilize your tomatoes and other plants with nitrogen-heavy fertilizers, as this nutrient helps promote plant development. When the plants start to flower and set fruit though, you want to back off with those mixes and incorporate a more balanced or “fruit and flower” fertilizer blend.

• Damaged Roots

  • Tomatoes (and all plants) intake most of their nutrients through their roots, so it’s possible that blossom end rot is a sign that the roots of the plant are damaged. This would be most likely to happen during transplanting.

• Soil Temperature

  • Temperature is also a factor in a plant’s ability to intake nutrients. If you sneak your summer crops in too early, the cool temps may be hindering them.

• Soil Issues

  • It’s possible your soil doesn’t have enough of the calcium the plant needs for fruit development, or your soil’s pH is off. Keep in mind that if this is the first year you’re seeing blossom end rot, this is unlikely, and it’s probably a result of one of the previous causes mentioned.

What can we do about it?

Right Away

• Pinch off the fruits with the rot. Have the plant focus on developing new, healthy fruits.

• Check you watering schedule. With blossom end rot, it’s most likely the soil is drying out too much between waterings. Make sure you’re watering deeply and consistently—you can dig down with a trowel to check moisture at the root level. In August, I usually have to water at least every other day. On the flip side, if your soil looks soggy most of the time, reduce your watering so the soil stays moist, not water-logged.

• Reduce your nitrogen inputs. Time to put away your fish emulsion, folks.

• Add calcium. A lower nitrogen fertilizer that includes calcium is a good swap. Bone meal or any organic tomato and vegetable fertilizer that includes calcium works well.

Long Term

• Promote healthy soil. Make sure to incorporate compost into your soil every spring or fall.

• Rotate your crops. Not all plants have the same nutrient demands at the same levels. Switching up the location of plants that rely heavily on calcium can give the soil time to regenerate.

• Try a new tomato variety. Some varieties may be more susceptible to blossom end rot than others. Trying new varieties can help you fix the problem, so long as you remember the ones you like.

• Check your soil temp. It’s tempting to plant your warm weather crops early to get a jump start on things, but starts put in soil that’s too cold for them may suffer throughout the season.

• Avoid working too close to your tomato plants to reduce the amount of digging you’ll be doing, and other potential root disruptions.

Need more info?

If you’ve tried these “quick fixes” and are still having problems, I recommend contacting the staff over at the Missoula County Weed District and Extension Office. They’re always a great resource, and can offer deeper insight into soil health.

Happy Gardening!