The Q&A Archives: Potatoes Never Matured

Question: What could be the reason for my disappointing Yukon Gold potato crop this year? The plants grew well and flowered, and I hilled them a couple of times. Then the foliage stopped growing and turned a bit yellow round Jul/Aug. I was expecting them to die off and find good sized tubers, but they never got past about the size of walnuts. I didn't see evidence of insects, although aphids found my tomatoes this year in the same garden. Last year was my inaugural potato season. Only 3 plants grew because I waited too long to plant the seeds, but the potatoes were wonderful, and yields heavy. They are in full sun and well drained, loose soil.

Answer: Well, it sounds as if you are doing everything right. Here's a few suggestions to think about for next year. As you probably know, when the tops of potato plants flower it usually indicates that the tubers are beginning to form. This is a critical time for watering, so keep the soil moist. After flowering is the time you can harvest 'new' potatoes. The longer the plants are alive, the larger the tubers will become. Normally when the tops yellow and die, the tubers are mature. It doesn't sound as though your potatoes went through the entire process. When you plant potatoes, use certified disease-free stock, and keep the plants watered well. Leave only a small portion of the growing vines exposed to encourage additional root development. Once the plants blossom, stop mounding up the soil. Sometimes too much fertilizer, especially nitrogen, will encourage the growth of the foliage at the expense of the tubers. Perhaps cut back on your fertilizing once the plants are about a foot tall, and see if that helps stimulate them to produce tubers.

Potatoes are succeptible to many fungal and some bacterial diseases and perhaps that was a factor. To reduce the potential for a problem, rotate them to a different bed each year. I hope some of this info helps!

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