We have had a lot of rain this spring, and some of our small kohlrabi are deformed and have yellow or tan scabs on one side. Also, some leaves are yellowing. What is causing this?

Gardens & Landscapes May 15, 2008 Print Friendly and PDF
Plentiful rains can cause mixed results in gardens. Good moisture promotes seed germination, and when it is warm and moist, plant growth can be rapid. Growing vegetables in sandy soil can be quite rewarding under such conditions, but in heavier soil, moisture can become excessive. Excess moisture can cause a plant problem called "edema" (or oedema), which, like it's namesake in humans, means too much moisture is being retained. In plants, water loss is mainly through the leaves. Sometimes, when the plant is awash in moisture, it develops these odd-looking things - crusty, scabby discolorations - that may all be on one side of the plant. Short of erecting a plastic tent over the garden, there are only a few things for you to do. A bit of cultivation with a pronged tool or hoe (provided it's not so wet that you create lumps) will help the soil dry out a bit. Increase spacing between plants if necessary by thinning, because good air circulation and full sunlight are important. If you mulched the affected plants, you might want to pull off the mulch if the soil does not dry out soon. The leaves and stems that are affected will never be pretty, but the plants should grow out of the condition if weather conditions improve. Edema will not spread to other plants. For more information read: M-323 - Oedema. The yellow leaves may also be symptoms of too much moisture. As the weather gets drier, the plants should add enough healthy leaves that the yellow ones won't be a problem.

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