Special Edition - Blossom End Rot

For this special edition episode/article of This Week in the Garden, I’ll cover something I’ve seen pop up in the garden this past week: blossom end rot. If you’re unfamiliar with blossom end rot, it can look like a serious disease. In this article/vlog, we’ll cover where it comes from, and why it isn’t a reason to be alarmed.

Blossom end rot emerges as a black, dark area on the “blossom end” of the fruit. It is most common on tomatoes, peppers, and watermelons, but can occur on a number of vegetables. Although symptoms look treacherous, this isn’t the end of your garden. Blossom end rot is caused by a lack of calcium in your plant, not a fungal or bacterial disease. For this reason, it won’t spread to other plants or even fruit on the same plant.

There are multiple reasons why plants would lack calcium. The first and most obvious reason is that there isn’t enough calcium in the soil. This isn’t particularly common though, especially if you add any fertilizers to the soil. The more probable cause is that the soil’s pH isn’t at the right level for calcium uptake. This can be difficult to do mid-season and is the rationale behind soil sampling. Soil samples are easy and free (most of the year) to do and help prevent a number of issues in the garden.

Other factors that can cause blossom end rot are inadequate moisture or improper fertilization. Too much or too little water can make it difficult for the plant to transport calcium from the roots to the leaves and fruit. Excess fertilization can cause plants to prioritize nitrogen and phosphorus rather than calcium, resulting in deficiencies. This is most common in tomatoes.

If you notice your plants are showing blossomed rot, remove affected fruit. Symptomatic fruit will not mature to harvest and are a waste of energy for the plant. To help prevent other fruit from being affected, make sure to consistently water and follow feralization recommendations. Foliar applied calcium fertilizers have shown inconsistent results as calcium is only taken up from the roots and transported thought the plant’s xylem. Similarly, soil-applied products are not necessarily helpful as calcium takes time before it can be taken up by the plant, and is often already available. However, a soil sample will definitively tell you if you need to add more calcium to the soil.

That’s all for this special edition article from This Week in the Garden. Here’s a helpful link if you have any questions about blossom end rot. If you’ve missed any articles check out our website where we keep them archived and fill out our form if you have any comments or questions. And of course, stay tuned until next time from This Week in the Garden.

-Adam