How to Prevent Blossom-End Rot on Tomatoes and Other Fruits

Blossom-end rot is a plant physiological disorder—meaning it’s caused by environmental factors rather than disease. It affects fruiting tomato plants, as well as peppers, cucumbers, melons, squash, and eggplants. Blossom-end rot appears when a fruit’s basal end fills with water, eventually turning brown and leathery before rotting. A little bit of blossom-end rot at the beginning of the season is a common problem—just remove the affected fruit to encourage plant growth—but persistent blossom-end rot can ruin an entire crop.

Calcium deficiency causes blossom-end rot in plants. There are a few factors that can prevent plants from attaining sufficient calcium levels:

1. 1. Soil moisture: Changes in soil moisture are the most common cause of blossom-end rot. When very wet weather at the beginning of a growing season is followed by a dry period with high temperatures, moisture stress can cause early-season blossom-end rot.
2. 2. Nitrogen levels: Too much nitrogen—often from fertilizer—can cause blossom-end rot, as the plant cannot accumulate enough calcium to keep up with its own rapid growth.
3. 3. Root damage: When hoeing near vulnerable plants, you may accidentally damage the roots, which makes it more difficult for plants to absorb calcium.
4. 4. Soil pH: Soil that is too acidic makes it harder for plants to access calcium present in the soil. The ideal soil pH is 6.5 to 6.8 for plants that are vulnerable to blossom-end rot.
5. 5. Soil temperature: Plants cannot absorb calcium well from cold soil.

Blossom-end rot is not a disease, so it can’t spread between plants. Since the disorder has to do with soil conditions, however, it will likely affect multiple plants in your home garden. There are a few ways to prevent blossom-end rot:

1. 1. Water: Keeping soil moisture levels consistent is one of the easiest ways to prevent blossom-end rot. Monitor rain and moisture levels, and give plants a thorough soak during dry periods to avoid drought stress. A soaker hose is a great way to make sure your plants are getting enough water.
2. 2. Mulch: Mulching helps retain moisture at the base of the plant. An added bonus: Mulch prevents weeds, meaning you're less likely to cause accidental root damage when weeding.
3. 3. Soil temperature: If you live in a colder climate, plant tomatoes and other vulnerable plants once the soil is fairly warm. Bring seedlings outside after any danger of frost has passed.
4. 4. Fertilizer: When choosing a fertilizer, look for formulas that are lower in nitrogen and higher in phosphorus and calcium. Avoid ammoniacal nitrogen altogether. Fertilize sparingly, and go especially light at the beginning of the growing season.
5. 5. Soil tests: A soil test will let you know whether your garden’s soil lands outside the 6.5 to 6.8 pH range. If it does, you can amend your soil with organic matter such as lime, gypsum, bone meal, and eggshells. Crop rotation is always a good idea for ensuring optimum soil health and keeping pH balanced.
6. 6. Records: It’s worthwhile to keep records of everything you plant. Over time, you may notice that certain tomato varieties are more vulnerable to blossom-end rot.

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