Despite all of their trials and tribulations, tomatoes are still the most popular vegetable (or to be botanically correct, fruit) grown in North America. Sometimes we may wonder early in the growing season why we go through all of the trouble, as there is a long list of potential problems that can plague the tomato. But, when we are finally rewarded with a vine-ripened fruit, dripping with tangy flavour, all of the past disappears and we are in love with the tomato once again.
Every year many tomato fans have difficulties with blossom end rot on their fruit and this summer of very warm temperatures and long periods without rainfall has produced even more than usual. Blossom end rot is the term that describes the dark, leathery sunken spot that develops on the bottom of otherwise healthy fruit.
From above the fruit looks perfectly normal. It is only upon closer inspection that the ugly scar is revealed. The tomato won’t ripen fully and properly when affected by blossom end rot, so you end up losing those fruits.
What causes this common problem? It’s not a bacterial or fungal disease as the name could imply. It occurs, rather, due to a lack of calcium in the plant. Calcium is one of those elements that plants don’t need huge amounts of, but they do require it. The problem comes not so much from a lack of calcium in the soil, but from a wide fluctuation in soil moisture.
When soil is dry, plant growth slows down and nutrients in the soil are far away from the area of uptake by the roots. When plants are watered growth is rapid, especially for plants like tomatoes, which don’t really have a very big root system relative to the size of the plant. The roots are unable to take up enough nutrients, including calcium, to supply the plant adequately. The result is blossom end rot. This situation is compounded by the hot, dry weather we’ve been suffering through, or enjoying, depending on your viewpoint!
An even supply of moisture is the best way to ensure that this doesn’t happen. Use a mulch of grass clippings or compost around the plants to keep moisture levels in the soil from fluctuating so widely. If you’re already using mulch, or you grow your tomatoes with black plastic mulch, or if you’re watering the plants every day, you may have leached all of the calcium out of the soil. Then you’ll need to replace it.
Egg shells, dolomite lime or bone meal are all good sources of calcium if mixed into the soil where you’ll be planting, but none of them work very quickly so don’t expect a miracle. You can also buy a liquefied calcium to spray onto the plants, but by the time you’ve discovered the leathery fruits it’s too late.
Even if you have lost a few tomatoes to end rot, don’t despair. Unless your watering woes are really severe it usually doesn’t last all season, and come September you’ll most likely have more tomatoes than you know what to do with anyway. I am thankful for the dark green thumbs of my parents who are presently supplying us with buckets of big meaty fruits that I’m turning into red sauce on a regular basis!

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