When to plant potatoes in Burns, OR

Start with certified seed potatoes

Potatoes are grown from pieces of tubers, so diseases and viruses travel with them. Certified seed potatoes are inspected and tested for these problems. Grocery potatoes may carry diseases, and some are treated to slow sprouting.

Cut large seed potatoes into pieces of about 1½ to 2 ounces, each with at least one or two eyes, and let them dry a day or two before planting. Pre-sprouting them in a bright, cool room for two to four weeks (called chitting) gives a faster, earlier crop.

Soil pH and scab

Potatoes tolerate acidic soil, with a pH of about 5.0 to 6.5. Common scab, the rough, corky patches on the skin, is caused by soil bacteria that are much less active at a pH of 5.2 or below. So don't lime before potatoes, and avoid fresh manure, which also encourages scab. Keeping the soil moist for the first several weeks after tubers start forming also reduces it.

Temperature and tuber formation

Plant when the soil is at least about 45°F; seed pieces sit idle or rot in colder, wet soil. Tubers form best when the soil is about 60 to 70°F and slow down when it's much warmer. Mulch helps keep the soil cool in hot summers east of the Cascades.

Hilling and green potatoes

Potatoes form on underground stems along the buried part of the plant. Hilling soil or mulch up around the stems as they grow gives more room for tubers and keeps them covered. Tubers exposed to light turn green. The green is harmless chlorophyll, but it signals that solanine, a bitter natural toxin, is building up too. Cut away green parts, and discard potatoes that are heavily green or taste bitter.

Water and late blight

Give potatoes about an inch or two of water a week, as evenly as possible. Uneven watering causes knobby, cracked or hollow tubers. Late blight, the same disease that hits tomatoes, can sweep through potatoes in cool, wet weather. Water at the soil, and if blight appears, cut and bag the tops and wait two weeks before digging so spores on the soil don't infect the tubers.

Harvest and storage

Dig new potatoes once the plants flower. For storage, wait until about two weeks after the tops die back so the skins thicken. Cure them for a week or two somewhere dark and humid at 50 to 60°F, then store them dark at about 40 to 45°F. Colder than that, potatoes turn some of their starch into sugar, which makes them taste sweet and brown too much when fried.