Potatoes can be harvested by digging carefully around the roots and gently pulling the plant out of the soil. (Photo by Kiki Fontenot)

Harvested potatoes come in all sizes. (Photo by Kiki Fontenot)

News Release Distributed 01/12/15

BATON ROUGE, La. – It’s the season for planting Irish potatoes in Louisiana.

“Potatoes are usually planted from mid-January through February,” said LSU AgCenter vegetable expert Kiki Fontenot.

The best way to plant potatoes is to dig a shallow trench about 4 inches deep, place sections of seed potatoes about 12 inches apart and then cover the trench, Fontenot said.

“People often cut seed potatoes too small, and they can rot if the soil stays wet too long,” she said. “Cut baking-size potatoes into quarters and small potatoes in half – about the size of a silver dollar. The bigger the piece, the better.”

Each piece should have at least one eye, which is the sprout that grows into a plant.

The old wives’ tale that potatoes should be planted eyes up isn’t necessary, she said.

Potato plants need plenty of room. “The bushes grow 2 1/2 to 3 feet tall and look perfectly manicured like mushrooms,” she said.

“The only thing you really need to do to get a good potato crop is to water and fertilize,” Fontenot said. An application of preplant fertilizer such as a 13-13-13 followed by another light application of fertilizer when the plants begin to bloom are all that are needed.

A light frost shouldn’t hurt the plants at all, and even with a freeze, only the tops of the plants will be affected, which may delay harvest.

Typically rainfall is plentiful in the early and late spring seasons to grow potatoes, she said. But if rainfall is sparse, especially during bloom when the tubers begin to form, an extra watering or two will help assure larger potatoes.

When the tubers begin to grow, some may peek out of the soil. The sun will cause the skin to turn green and produce alkaloids, which can cause stomach distress if they’re eaten. To prevent this, draw soil from the sides of the rows and mound it around the bottoms of the plants, Fontenot said.

“If you’re growing potatoes in raised beds or containers, you can get a bag of soil to add to the planter,” she said.

An alternative to mounding soil is to lay down a heavy mulch, like leaves, she said. But light mulches like pine straw won’t work because they allow sunlight in.

When the plants develop brown tops – 50 percent or more – the potatoes are ready to dig. That’s generally 90 to 110 days after planting.

“If weather forecasts predict rain for a long term, it’s best to dig the potatoes small rather than allow them to remain in saturated soil where they may rot,” Fontenot said. “This is especially true in heavy soils that don’t drain well. Smaller potatoes are better than none.”

At harvest, Fontenot recommends digging wide to avoid damaging potatoes in the soil. “Use a spade or fork and start at the drip line,” she said. “Then pull and shake the plants to remove the soil. A few potatoes may drop, but many will stay attached to the plant. Be gentle.”

Fontenot said recommended varieties for Louisiana are Red LaSoda – a red-skinned potato – and Kennebec – a brown-skinned tuber. Others include Golden Yukon, which has a yellow flesh, and Purple Majesty, which has a purple skin and flesh. Both do well in Louisiana, Fontenot said.

Many varieties can produce well in the state, but most nurseries and garden centers carry only a limited selection. Other varieties are available from certified growers by mail order.

Fontenot warned that although purple potatoes look great and are fun to grow, the color leaches out when the potatoes are boiled or steamed. “They look gray,” she said. But if they’re fried or baked into chips, they are more likely to maintain their color.

“Potatoes are easy to grow,” Fontenot said. “I’ve never had a problem growing potatoes.”

The only insect problem is the Colorado potato beetle, which feeds on the foliage.