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The disorder shown here is called 'hollow heart,’ and potatoes affected by it are safe to eat once the damage has been cut away. Special to Forum News Service

Potato disorder affects tuber's interior

Q: I have a question about the potatoes that we grew in our family garden. This year some of our russets and Red Pontiacs have bad spots in the middle of the potatoes. Not all tubers have the problem, but we've had to throw some that were totally unusable. What causes this, and what can we do to prevent it in the future? — Paul Meyer, Fargo.

A: The disorder is called 'hollow heart,' and affected tubers have voids or cracks in the middle, which are sometimes brown and discolored. When I was with North Dakota State University, we used to joke that hollow heart was a good thing in russet baking potatoes because the voids gave a spot to hold the butter and sour cream.

Some of our garden potatoes also have hollow heart this year. We've cut open very nice potatoes, only to find the center is ruined. The outside of the tuber usually shows no symptoms. Potatoes with hollow heart are safe to eat, and damage can be cut away if enough of the tuber is left.

Instead of being caused by disease or insects, hollow heart is called a physiological problem. According to university extension services, the exact combination of causes isn't completely understood, but it happens through interactions of weather, air and soil temperature, soil moisture, cultivar, plant spacing and available nutrients. Hollow heart seems to be worse when a period of rain follows a dry spell.

Tubers might react to the sudden moisture increase by a quick spurt of growth, which cracks the center open, similar to the cracking that happens in tomatoes and carrots when rain follows dryness. Commercial potato growers minimize hollow heart risk by carefully monitoring soil moisture and fertility.

To avoid hollow heart, maintain even soil moisture, avoiding fluctuations. Mulching with straw or grass clippings can help.

Q: I know maples often do poorly in heavy clay soil. Is there another tree with nice fall color that might be better adapted? — R. Larsen, Grand Forks.

A: Prairie Torch Buckeye, developed by NDSU, and Autumn Splendor Buckeye, developed by University of Minnesota, both have great fall color: orange-red with golden tones. These varieties of buckeye become full-sized shade trees and are better adapted to soil types throughout North Dakota and Minnesota. A fascinating brand-new buckeye from NDSU is called Lavaburst, which, I hope, will be available in the near future.

Q: The stems of my African violet leaves get soft and rot where the stems touch the rim of the clay pot. Is there a way to prevent this? — April Felton, Alexandria, Minn.

A: Clay pots are ideal for most houseplants, but the juicy stems of African violets are sensitive to the minerals that tend to accumulate on the rim of clay pots. Many violet growers choose plastic or ceramic pots instead, or coat the rim of clay pots with aluminum foil or dip them in canning paraffin.