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Wednesday, August 21, 2019  Spokane, Washington  Est. May 19, 1883
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In the Garden: It’s a cool time to grow potatoes again

Potato plants look attractive in the vegetable garden and yield buried treasure in the fall. (Susan Mulvihill)
Potato plants look attractive in the vegetable garden and yield buried treasure in the fall. (Susan Mulvihill)

Potatoes are one of the most enjoyable cool-season crops to grow. Not only are the plants attractive but it’s also great fun to dig for buried treasure in the fall.

For years, I thought potato-growing was a snap. Unfortunately, I had a rude awakening three years ago while growing Yukon Golds and Rose Finn Apple fingerlings.

All of the plants were lush and beautiful early on, but then they started to look stressed. There were small brown spots on the leaves that steadily grew larger and the plants died prematurely. A friend of mine who was also growing Rose Finn Apple potatoes that year had the same problem.

It’s likely the plants had Late Blight, a fungus that can develop from diseased potatoes. I always buy potatoes that are certified to be disease-free from local garden centers or online so am unsure why this happened. It’s hard to say if the cool, wet season that year contributed to the problem but it probably didn’t help.

After some research, I learned it would be smart to stop growing potatoes for a couple of years to avoid more instances of that disease.

This year, I finally get to grow them again. Potatoes are members of the nightshade family, as are tomatoes, peppers and eggplants. Rotating where we grow crops in the same plant family is a way to avoid insect and disease problems. This means potatoes shouldn’t be planted in beds where any nightshade crops have been grown in the previous three years.

Traditionally, potatoes are planted on Good Friday, which came early this year, but the early to middle part of spring is best. I used to buy large seed potatoes and cut them into chunks containing a minimum of two “eyes,” which is where the sprouts will grow from. Then I’d place the chunks on a sheet of newspaper for a day to let them dry out so there was less chance of them rotting in the soil. Even with that precaution, I would occasionally lose one or two to rot.

A few years ago, I realized it would be smarter to purchase small seed potatoes and plant them whole. That eliminated the rot problem and I learned the size of the seed potato has no bearing on the size of potatoes I would harvest.

Seed potatoes can be found at local garden centers or from online businesses like Irish Eyes Garden Seeds (, which has a wide variety of organic tubers. Some varieties with good disease resistance are All Blue, Carola, Kennebec and Sante.

Seed potatoes should be planted 4 to 6 inches deep and a foot apart. Amend the soil with compost rather than manure, which can encourage potato scab. The plants like well-drained soil and regular watering.

When they reach about a foot in height, you can either add soil around the plants or surround them with a thick straw mulch. Either method will keep potatoes growing near the surface from getting hit with sunlight. This causes the tubers to manufacture solanine – a natural toxin found in green potatoes – which can be harmful to eat.

When the plants start blooming, you can carefully dig up a few new potatoes which are a wonderful summertime treat when paired with fresh parsley and melted butter.

In early fall, once the foliage has died back from frost, it’s time to harvest the tubers. They should be placed in a dark area that is between 50 and 60 degrees for about two weeks, then stored where the temperature remains below 50 degrees.

Susan Mulvihill can be reached via email at her blog at for more gardening information, tips and events.

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