What Is Blossom End Rot?
Blossom end rot is not a fungus, bacteria, or other disease. It is not caused by an insect or other animal pest. It is a physiological disorder that begins during the early stages of fruit development. If you’ve ever grown tomatoes, and discovered one or more with a black, circular, possibly sunken patch on the bottom end where the flower parts fell away from the young fruit, it was suffering from blossom end rot. Tomato plants are famous for developing blossom end rot, but it is sometimes seen in other garden veggies like peppers, squash, and cucumbers as well.
What Causes Blossom End Rot?
Blossom end rot is technically caused by a calcium deficiency in the developing fruit. However, the fix isn’t as simple as adding lime to the soil or spraying liquid calcium on the leaves. In most native soils there is plenty of calcium to support an abundant crop of healthy tomatoes. The problem is that under certain conditions garden plants are not able to uptake the existing calcium. The real key to solving blossom end rot is water.
Plants need plenty of water in order to pull calcium from the soil. Often, the earliest tomatoes develop just fine, because they formed while temperatures were cooler and soil moisture was more plentiful. As summer progresses, temperatures increase, plants grow and need more moisture just to survive, even as less moisture becomes available. When that happens, the plant is not able to carry enough of the existing calcium to the developing fruits.
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Other Causes of Blossom End Rot
There are other scenarios that can lead to blossom end rot. Root damage that occurs during transplanting or while cultivating can decrease the plant’s ability to take up water and nutrients. Soggy soil interferes with roots’ ability to absorb calcium. Excessive fertilization can damage roots as well. It is also possible the soil is indeed lacking in calcium.
How to Prevent Blossom End Rot
Blossom end rot does not spread from plant to plant. If it develops, simply remove the affected fruit immediately. Doing so frees up the plant to produce new fruit, rather than wasting energy to ripen the damaged ones. Here is how to prevent blossom end rot in your garden:
- Get the right soil balance. Grow tomatoes in moist, well drained, highly organic soil. Maintain a slightly acid soil pH between 6.5 and 7.5. The best fertilizer for tomatoes is low in nitrogen, but high in phosphorus (something like 5-10-5). In order to determine your soil nutrient needs it to perform a soil test. You can get test kits at your local home improvement store or garden center. Or, contact your local extension office for soil testing information. Once you know the nutrient level in your soil, you can add lime and fertilizer as recommended by a soil test.
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- Cultivate the soil correctly. Avoid deep or aggressive cultivation near the base of the plants after fruits begin to develop, especially in hot, dry weather. Pull weeds by hand, or lightly scrape the soil surface with a hoe.
- Water consistently. Above all be sure to supply consistent water. Your garden needs 1 to 1.5 inches of water per week, throughout the growing season. If you can not hand water consistently, consider installing a soaker hose. The soil should always feel like a wrung-out sponge. Apply a liberal amount of organic mulch to help retain moisture.
Blossom end rot is a bothersome part of gardening, but thankfully it is easily preventable. Give your plants a healthy growing environment and closely monitor their development, and blossom end rot will be a problem of the past.
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