Blossom End Rot in Tomatoes: Causes, Prevention, and Treatment Guide

By Marcie

Blossom end rot is a physiological disorder that commonly affects tomatoes. It is characterized by a dark, sunken, and leathery spot at the bottom of the fruit, which eventually leads to fruit rotting and falling off the plant. This can be frustrating for gardeners who have put in a lot of effort into growing tomatoes, only to have them ruined by this disorder. It can be very disheartening when you spot this ugly stuff on your tomatoes. Let's take a deep dive into what causes blossom end rot, how to prevent it, and how to treat it if it should happen to rear its ugly head in your garden.

Causes of Blossom End Rot

Blossom end rot is caused by a lack of calcium in the fruit. Contrary to popular belief, it is not caused by a lack of calcium in the soil. In fact, calcium is present in most soils in sufficient amounts. The real problem is a lack of water or an imbalance of nutrients that prevent the plant from absorbing calcium. When the fruit is growing rapidly and requires a lot of calcium, but there is not enough available, the fruit may develop blossom end rot.

Several factors can contribute to blossom end rot. One of the most common is uneven watering. When the plant experiences dry periods followed by a sudden influx of water, it can disrupt the calcium uptake process. As a result, the fruit may not receive the calcium it needs to develop properly.

Another factor that can cause blossom end rot is soil pH. Tomatoes prefer a slightly acidic soil with a pH between 6.0 and 6.8. If the soil pH is too high or too low, it can prevent the plant from absorbing calcium. In addition, excessive use of fertilizers, especially those high in nitrogen, can contribute to the development of blossom end rot.

Preventing Blossom End Rot

Preventing blossom end rot is much easier than treating it once it has already occurred. Here are a few tips for preventing this disorder from affecting your tomato plants:

1.Water the plants regularly and consistently. Avoid letting the soil dry out completely or become waterlogged. If you are using containers, even large ones, make sure there is plenty of soil drainage.

2.Mulch around the plants to help retain moisture in the soil. You can use mulch, I don't use mulch very much.

3.Ensure that the soil pH is within the preferred range for tomatoes. I don't normally check soil unless I am having issues with the plant itself. I use a potting soil, so I know that the soil is already up to par for planting.

4.Use a balanced fertilizer that is not too high in nitrogen. I would talk to local gardeners about the fertilizer used locally. Contacting your local extension office would also be a good resource.

5.Avoid over-fertilizing the plants. Too much fertilizer can disrupt the nutrient balance in the soil, leading to calcium uptake problems. I buy soil that usually has some fertilizer in it, and that gives it a boost!

How To Treat Blossom End Rot

• Remove any affected fruit from the plant. This will help prevent the spread of the disorder to other fruit on the plant.
• Water the plant thoroughly and consistently to help it absorb more calcium.
• Apply a calcium supplement to the soil or directly to the plant. There are several products available that are specifically designed to treat blossom end rot.
• If the soil pH is too high or too low, adjust it to the appropriate level.
• Avoid using fertilizers high in nitrogen, as they can exacerbate the problem.
• Consider using a foliar spray that contains calcium to help the plant absorb more of this nutrient.

I don't normally use a calcium or foliar spray to treat blossom end rot. If I get a plant that has multiple tomatoes with blossom end rot, I pull the plant up and start over.

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