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Ask a Master Gardener: Seed potatoes sprout too soon

Gardeners in the Northland may find their seed potatoes sprouting before they can be planted.

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Q: I bought some seed potatoes by mail and stored them in my basement. They grew long sprouts. Can I still plant them?

A: Yes, you can.

Potatoes
The University of Minnesota Extension recommends buying certified disease-free seed potatoes that are firm and that have not sprouted.
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Extension recommends buying certified disease-free seed potatoes that are firm and that have not sprouted. Potatoes that have already sprouted when they’re planted may have a lower yield.

The trouble is that if you don’t order potato seed early, the seed companies run out, especially of unusual kinds. But if you do order early, it’s hard to store potato seed properly until it’s warm enough outside to plant in northern Minnesota. Seed potatoes should be stored at temperatures between 38 and 40 degrees, and many of us just don’t have the right place to keep them. A basement is too warm.

So we northern gardeners often end up with sprouts on our seed potatoes.

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It was tough to find good, research-based information about what to do in that case, so I consulted St. Louis County horticulturist Bob Olen. He told me that you can still try planting them.

“You can lay the spouting stem just under the soil surface, but if it has leaves these should be just above the surface,” he said in an email. “Do this very carefully. Do not break off the stem.”

The stems tend to be brittle, so you’ll need to handle the potatoes gently. “Often the problem is timing.” Bob said, “because any leaf tissue above the surface is vulnerable to frost and at this time we are a long way from frost-free planting.”

If your sprouts do have leaf tissue emerging, you may want to take some special precautions.

“Tubers could be planted in containers, which could be moved indoors” in case of frost, Bob said. Or, you could have some kind of cover ready to put over your potatoes if they have leaves above the surface and a frost is predicted.

“I have done this successfully, but it does require some diligence,” he said.

Bob said if he were in your shoes, he’d give planting the sprouted potatoes a try, but he would also plant some new seed potatoes to make sure to get a crop.

Written by U of M Extension Master Gardeners in St. Louis County. Send questions to  features@duluthnews.com .

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