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Wednesday, September 30, 2020  Spokane, Washington  Est. May 19, 1883
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Nourish tomato roots with careful watering

Calcium deficiency is the underlying cause of tomato blossom end rot.
Calcium deficiency is the underlying cause of tomato blossom end rot.
Pat Munts

What’s wrong with my tomato? This seems to be the most popular question asked of the WSU Master Gardeners in the past couple of weeks. Usually the question comes attached to a handful of almost-ripe tomatoes with blackened or mushy bottoms. Ah, yes, tomato blossom end rot has appeared in all its glory.

Blossom end rot appears on tomatoes and other vegetables as a tan or black leathery patch at the blossom end of the fruit about the time it starts to ripen. It isn’t caused by bugs, disease or fungus, so spraying it with insecticides won’t do anything for it. Rather it’s a physiological disorder created by a calcium deficiency brought on by poor root development and/or consistent watering during rapid plant growth.

We are seeing a lot of it this summer because the weather was too cold for good root growth early in the summer. As a result, when the warm weather did arrive and the plants began growing rapidly and setting fruit, there weren’t enough roots to support them. Human error came into play when the hot weather hit and we didn’t realize the plants needed more water than they had been getting even with the cooler-than-usual temperatures.

Cultural controls of blossom end rot involve using properly hardened off transplants in the spring, planting when the soil temperature is higher than 65 degrees, mulching the plants to help even out soil moisture between waterings and being attuned to the water needs of the plants when they put on growth spurts.

Once blossom end rot has appeared, its impact can be reduced by using a fertilizer low in nitrogen but high in superphosphates, such as a 4-12-4 or a 5-20-5 mix. There are foliar sprays available, but they must be used carefully and are not a substitute for good soil management. Regardless of what methods you use, changes will take a little time to become evident. If it is a persistent problem in your garden, it may be time for a soil test.

Got lots of green tomatoes? Not that I’m a pessimist, but we are running out of warm weather to get them all ripe before the frosts hit. Tomatoes that are beginning to turn color can be picked and placed in a shallow box in a dry place. They will ripen over a few weeks, extending your BLT sandwich season. The green fruit can also be pickled or turned into relishes for winter use. Just remember to use current recipes and processing techniques if you can them.

Recently I was in Atlanta and got my first taste of southern fried green tomatoes. I had always wanted to try them, and being in the region that made them famous was the perfect way to sample them. They were tasty! I will be trying a few recipes with my green tomato crop as they ripen. Here is a good website with some of the recipes I am going to try:

Pat Munts is a Master Gardener who has gardened the same acre in Spokane Valley for 30 years. She can be reached at pat@inlandnw
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