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Q: We planted a tomato plant in May and we have quite a few tomatoes. The problem is now the bottoms of the tomatoes are turning black. Any idea why this is happening?
A: The problem is called blossom end rot. We have talked about this in the past but I am getting quite a few emails about this at this time. So we will revisit the issue again. It is caused by a lack of calcium uptake by the plant. It is not due to a calcium deficiency in the soil as we have enough calcium in the soil in our area so there is no need to add calcium we just need to get it into the plant. This is accomplished with watering and the timing of the watering. The factors affecting the lack of uptake of calcium are:
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• Lack of steady moisture during periods of drought. It is critical to keep tomatoes/zucchini moist at all times, and this is especially true when the fruits are setting and developing. For example, using a clay pot in a hot location could be a contributing factor. Clay pots are notorious for drying out more quickly than plastic pots because the clay is much more porous.
• The plant needs calcium to develop fruit properly and that calcium is dissolved in soil water. If water is lacking then so is the calcium. Thus, you can have a calcium deficiency and yet have a good source of calcium in the soil. You can test your soil to make sure you don’t have a calcium deficiency. Simple soil test kits are available in most garden centres.
• Rapidly growing plants are more prone to the problem because fast growth requires an abundant supply of water and calcium. Also, excess nitrogen from overfertilizing can contribute to the problem by excessively speeding up growth.
• Transplanting tomatoes into cold soil may contribute to calcium deficiency because the organisms that convert calcium into a usable form are not as active in cold soils.
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• Cultivating deeply around tomatoes can damage roots and cause a lack of water and calcium uptake.
I’m sharing a story from our house to yours. My lovely wife Julie cannot kill a slug so she caught one recently and put it into our weed bin that we keep in the garage. She said she wanted to keep it happy by putting it in the weeds. That night the slug climbed out of the bin and left lovely silvery slime trails all over the garage floor! Enjoy your gardening!
Every week, Growing Things Outdoors runs online at edmontonjournal.com or, if you prefer an epaper format, epaper.edmontonjournal.com
Learn more by emailing your questions to filipskigerald@gmail.com, reading past columns or my book Just Ask Jerry. You can also follow me on X, formerly Twitter, @justaskjerry01.
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