A primer on potatoes

By JUANITA BOUTWELL
UC Master Gardener

I grew up in potato country — not Idaho, but south central Colorado, where the farmers grow mainly potatoes and barley. So we ate potatoes at least once a day. But I had never eaten fresh, organic, home-grown potatoes until I started growing them a few years ago. What a treat!

 Potatoes are my favorite crop, not only because they taste so good but also because they are so easy. Many different varieties are available now by mail order. You can choose types that store well or that produce early “new” potatoes. You can grow waxy fingerling types or  potatoes in different colors, including yellow and purple.

In Napa Valley, potatoes can be planted in March and April or in July and August. You can plant different varieties at different times. For example, you could plant late-maturing types in March, then some that have a short production time in summer to have new potatoes by fall.

It’s important to start with certified disease-free seed potatoes. Seed potatoes are just mini potatoes from the previous year’s crop, not true seeds. They should be about the size of a golf ball and have at least one eye.

Saving potatoes from the previous year to use as seed is not a good practice, as they can potentially pass diseases along to your new crop. Don’t even think about planting potatoes from the grocery store because they are often treated to inhibit sprouting.    

Prior to planting, you can pre-sprout or “chit” your seed potatoes. About two weeks before planting, spread the potatoes out in a single layer in an area with low light. If you have some larger seed potatoes, you can cut them into two or three pieces. Do this a day or two before planting to give the cut surface time to heal.

Occasionally, potatoes rot before they sprout. Chitting gives them a head start, and making sure any cuts have healed will help prevent rot as well.

Potatoes like very loose, well-drained soil. Dig a furrow, leaving a ridge of soil to the side. Plant the potatoes in the furrow, cover with just a little soil and water well. If possible, avoid watering again until the potatoes sprout to reduce the likelihood of rotting.

As the leaves emerge, begin mounding the plants with soil from the ridge, leaving just a few leaves exposed. The new potatoes will form above the seed piece, so mounding with dirt, or “hilling,” ensures that the new potatoes will be protected from the sun. Repeat the hilling a couple of times as the plants grow to prevent exposure to sunlight, which causes potato skins to turn green. The green skin is toxic if consumed in large quantity. 

When the plants start to decline, the potatoes are ready to harvest.

You can also plant potatoes directly in a bag of potting mix, and they do well in containers. I have seen towers made of wire fencing with holes large enough to allow the leaves to poke through. As the potatoes grow, keep adding soil or compost to the tower.

My favorite way to plant potatoes is in a raised bed under straw. First, I make sure the soil is well watered. Then I add a layer of compost and water again. I then cover everything with a thick layer of newspapers and wet the newspapers well. I place the potatoes about one foot apart and poke holes through the paper underneath the tuber. I then cover everything with about four inches of straw and water well. Then I try not to water again until I see the shoots poke through.

The newspapers, compost and straw hold moisture well, so I don’t need to water as much in summer. Planting under straw also makes it easy to steal a couple of potatoes for dinner without disrupting the whole plant. I just push aside the straw, grab some potatoes, then cover everything  up again. 

This method also builds fabulous soil. The following year, it will be rich and crumbly from the decomposed compost and straw. To keep soil-borne diseases from establishing, don’t plant potatoes, tomatoes, or peppers in the same bed again for three years.

About the only serious potato pest is gophers. They adore potatoes. Protect your plants somehow, either by lining the bed with hardware cloth or by planting in containers.

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