Growing Potatoes in Oregon and Washington

Potatoes are one of the most productive crops you can grow in a small space, and they like the Northwest's cool spring weather. Digging them up is like a treasure hunt, which makes them a favorite with kids.

When to plant

Potatoes go in during spring, a few weeks before the last frost, once the soil can be worked and isn't soggy. The shoots can be nipped by a late frost, but the plants usually regrow from below ground.

• Portland: Mar 15 – Apr 26. Details.
• Spokane: Apr 15 – May 27.
• Bend: May 12 – Jun 23.

Start with certified seed potatoes

Buy certified seed potatoes from a garden center or seed company. They're grown to be free of the diseases that can build up in soil, and they haven't been treated to stop sprouting the way many grocery-store potatoes have.

Small seed potatoes can go in whole. Cut larger ones into chunks about the size of a golf ball or a bit bigger, each with at least one or two eyes (the small buds). Let the cut pieces sit for a day or two so the cut surfaces dry before planting.

Planting

1. Choose a sunny spot with loose soil. Heavy, wet soil can rot seed pieces in a cold spring.
2. Dig a trench about 4 inches deep.
3. Set the pieces cut side down, about 12 inches apart, with rows 2 to 3 feet apart.
4. Cover with soil.

Avoid adding fresh manure or lime right before planting. Both can encourage potato scab, a disease that leaves rough, corky patches on the skin.

Hilling

New potatoes form along the buried stem, above the seed piece. When plants are 6 to 8 inches tall, pull soil, compost or straw up around the stems, leaving the top few inches of leaves showing. Repeat once or twice as they grow. Hilling gives the potatoes more room to form and keeps them covered. Potatoes exposed to light turn green, and green skin should be cut away before eating.

Water regularly once plants are up, especially while they're flowering, when the tubers are forming.

When to dig

• New potatoes: start gently digging around the edges of plants a couple of weeks after they flower. Take a few and leave the rest to grow.
• Storage potatoes: wait until the vines have yellowed and died back, then leave the potatoes in the ground about two more weeks so their skins toughen. Dig on a dry day, and handle them gently.

Let storage potatoes cure in a dark, airy spot for a week or two, then store them somewhere cool, dark and humid. Keep them away from onions and out of the light.

Rotate where you plant potatoes each year, and avoid following tomatoes, peppers or eggplant, which share some of the same diseases.