Seed Potatoes - planting and culture

Most varieties of potatoes can be grown in the Northwest. We've selected varieties that do exceptionally well and are proven performers. The ideal climate for raising potatoes is one with cool, moist summers. While the Puget Sound area has the cool temperatures, adequate water must be provided during our typically dry summers to keep tubers from drying out. Always use nursery-selected seed potatoes. Do not try growing plants from potatoes purchased at a grocery store. They may carry disease and are often chemically treated to prevent sprouting.

SOIL

Potatoes need a rich, loose, slightly acid soil with a pH of about 5.4 to 6.6 (if soil is not acidic enough, scab disease may occur). Potatoes are adaptable and will usually do well even if the soil is less than perfect. However, they thrive in high levels of organic matter, such as mature compost. Remember that too much nitrogen (N) will produce lush, leafy vines but few tubers, and too much potassium (K) produces tubers with less protein.

PLANTING

Small potatoes (about the size of a hen’s egg) should be planted whole. Large tubers can be cut into pieces, with each 3 to 4 ounce piece having at least two strong eyes. Use a clean, sharp knife and let the pieces heal over for a day before planting. Don’t allow pieces to dry out or sit in direct sunlight. A dusting of powdered sulphur is recommended before planting. Pre-sprouted potatoes encourage early growth, so be careful not to break off these sprouts.

Optimum soil temperature is between 55 and 70ºF. In the Pacific Northwest, 10 days to 2 weeks before the last frost date should be a safe time to plant.

Home gardeners can plant in shallow trenches about 6 to 8 inches deep with as little as 2 feet between each trench. Space the seed pieces (or small potatoes) 10 to 12 inches apart and cover with 3 to 4 inches of soil.

When plant stems grow to about 8 inches high, mound to about 4 inches with soil from both sides of the trench. This is called “hilling.” As the plant grows, repeat this several times in 2 to 3-week intervals during the growing season. Make sure there is enough soil on the mound to keep the tubers covered. Once exposed to light, they will become green-colored and inedible!

WATERING & FERTILIZING

Potatoes need a steady supply of moisture but will rot in cold, waterlogged soil. It is thought by some growers that plants struggling for water may produce fewer, smaller, disfigured potatoes but with better taste. Growers agree, however, that weeds must be removed for best production. During the growing season we recommend an organic foliar spray such as seaweed extract — easy to apply and excellent for growth. For best results, apply it in the morning and stop use once plants are in full bloom.

HARVESTING & STORAGE

“New” potatoes are not a variety, but merely any potato lifted before maturity. Small and tender, they are harvested while plants are still blooming. Other potatoes are harvested after plants are finished blooming. Leave the tubers in the ground for 10 to 14 days to “cure.” Their skins will toughen up and they’ll be ready to harvest. Harvest potatoes in the morning while it is cool.

Store potatoes in the dark at 36 to 40ºF with enough air circulation so they can “breathe” (after all, they’re alive!). Place them in burlap sacks, baskets or crates, and do not store them with apples (which give off ethylene, possibly causing the potatoes to sprout).

TIPS

If you have had chronic insect problems, consider planting a “sacrificial” plant, such as eggplant, nearby. Beetles will prefer the eggplant, making it easy to pick off and destroy the beetles and their eggs. Bacillus thuringiensis (Bt) is an effective botanical control, but only for insect larvae. This bacteria will not harm humans and other animals, but will begin a control cycle for beetles.

No room for rows? Don’t give up the flavor of homegrown potatoes. Start with any deep container and fill the container with soil as the plant grows. You can grow plenty of potatoes in a relatively small space. It’s wise, however, to have a plan for dealing with the excess soil once the potatoes are harvested.

Or you can grab a clean garbage can and cut drainage holes in the bottom. Use this as your planter. Fill the bottom third with soil and adding more as the plants grow. Try 3 plants per can.