Patience for Planting Potatoes
Chances are that some dedicated gardeners have already tilled their gardens and planted their "seed" potatoes, their aim to plant on or around St. Patrick's Day. But with all the recent rains and flooding, many of us will be lucky to have them planted by Mother's Day!
Because our weather can be so unpredictable, it's hard to be very precise about planting time. Potatoes are considered to be a cool-season crop and can be planted just as soon as the ground has thawed and dried enough to safely work the soil. But it is critical to allow the soil to dry adequately. If worked while it's still too wet, soil becomes hard and compacted, leading to long-term frustrations for the eager gardener.
The potato plant can adapt to most types of soil but must have good drainage to prevent the tubers from rotting before they can be harvested. The part of the potato plant that we eat is called a tuber, a technical name that refers to an enlarged modified stem that grows underground. Potato tubers that are used to create a new planting are called seed potatoes. You'll want to start with the best quality seed potatoes, so look for those that are labeled as "certified disease-free" at garden shops and in mail-order catalogs.
To start a new planting, choose a sunny, well-drained location and work in a moderate amount of organic matter and 2-3 pounds of a balanced, low-analysis fertilizer, such as 12-12-12 per 100 square feet, to promote vigorous plant growth. Potatoes grow best in acidic soil, pH below 5.2 if possible, to prevent infection of potato scab fungus. If possible, plant in a different bed than where potatoes were grown last year.
Cut the seed potato into pieces so each individual piece has at least one healthy-looking bud (often called an "eye"). That bud will become the shoot of the new plant and, as the stem develops, it also will produce new roots. The piece of tuber attached to the bud provides a source of carbohydrates to sustain the young plant, until those new roots and shoots develop. Plant the pieces 2-3 inches deep, spaced about 12 inches apart within the row and 24-36 inches between rows.
New tubers that will become this year's harvest generally begin to form sometime in early to mid-summer and continue to grow in size until early fall, as long as adequate moisture, air and nutrients are available.
The tubers can be harvested as "new" potatoes in mid- to late summer, before they reach full size and before the skins start to toughen. If you want bigger yields of full-size tubers, it's best to leave the plants until they begin to die back on their own, usually by late summer or early fall.
For more information on raising, harvesting and storing potatoes, see Purdue Extension Bulletin HO-62 http://www.hort.purdue.edu/ext/HO-62W.pdf.