Watch out for Blossom End Rot

Among the many different kinds of veggies that I planted in my garden this year, tomatoes are one of my favorites. I planted several different heirloom varieties including Brandywine, Blue Berries, Beefsteak, Chadwick Cherry, Roma, Green Zebra, Moneymaker, Yellow Pear, Arkansas Traveler, Bradley, Black from Tula, Indigo Rose and Orange Plum — all are doing very well so far – but sometimes, heirlooms have less resistance to diseases and disorders. In the past, one of the issues for my tomatoes was Blossom End Rot. It has been a few years since this was a problem, but those varieties most affected were Beefsteak and Roma.

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When the weather warms up, the tomatoes begin to set fruit, but as the tomatoes grow they sometimes develop Blossom End Rot. The symptoms of Blossom End Rot are found at the blossom end of the tomato (opposite end from the stem). The area gets a water-soaked appearance, which gradually gets bigger and turns brownish or blackish and looks leathery, and the end of the tomato will appear flattened. There are a number of causes for Blossom End Rot, and all are easily remedied.

The most common cause is calcium deficiency. When the weather gets hot and dry, the tomato plants draw extra water and nutrients to their leaves, which can starve the fruits of calcium. Calcium can also be leached away with heavy rainfall or excessive watering. We don’t have a big problem with heavy rainfall here in the High Desert, but it is easy to readjust the amount of irrigation water the plants receive. The soil should be moist, but not soggy. Adding a quality low-nitrogen fertilizer that has calcium in its list of ingredients can help to boost the calcium available to the plant. Too much nitrogen causes the plant to have too much green growth at the expense of the fruits.

Also, if the soil’s pH is too high or low (best range is 6.0 to 7.0), the calcium in the soil may not be available to the plant. You can add horticultural limestone/lime to soil that has too low of a pH. If the soil is not excessively acidic, add some gypsum. If your soil has too high a pH, add sulfur according to the package directions. If your garden is like mine and contains no native soil at all, the pH could be a bit on the low side. If your soil is mostly native desert soil, it may be a bit on the high side. Test your soil and adjust it accordingly.

Another problem that can cause Blossom End Rot is uneven watering — the soil gets really wet after watering and dries out too fast because the soil does not retain the moisture sufficiently, which is a common issue with our High Desert soils. The best remedy is to add a thick layer of organic matter such as compost to the soil and cultivate it carefully, trying not to disturb the plant’s root system. It should help to provide good drainage, while helping the soil to maintain a more even moisture level.

In the case of my Beefsteak plant, it was probably suffering from a couple of calcium deficiency problems that were causing the Blossom End Rot condition. Although the plant received adequate sunlight, it was receiving a little more shade than the other tomato plants, but I had been watering it just like the others. There was a chance it was getting over watered, and perhaps leaching the calcium from the soil. This variety may also have been less resistant to Blossom End Rot than my other tomatoes.  I cut back on the watering just a bit because I noticed the Blossom End Rot occurred after I watered the garden heavily to make sure it didn’t dry out while I was on a weekend get-away. The rest of the garden dried out sufficiently, but not as much where this tomato plant was located.

My soil is probably 99 percent organic matter and contains no native desert soil at all, so there was a chance the pH was a little low. I should have done a simple pH test to know for sure. A purchased a bag of organic bone meal, with an analysis of 4-12-0, did take care of the problem. There is a small amount of nitrogen and a fair amount of calcium in the ingredients list, plus the extra phosphorus helps the plant to have a stronger root system and get more blooms, thus more tomatoes. This, along with watering a little less, not only remedied the calcium deficiency problem, I got more tomatoes to boot.