The Vegetable Garden

    Potato, Irish

      Potato is a cool-season vegetable that ranks with wheat and rice as one of the most important staple crops in the human diet around the world. The white potato is referred to as the "Irish potato" because it is associated with the
      potato famine in Ireland in the 19th century. Potatoes are not roots but specialized underground storage stems called "tubers." Maximal tuber formation occurs at soil temperatures between 60° and 70°F. The tubers fail to form when the soil temperature reaches 80°F. Potatoes withstand light frosts in the spring and can be grown throughout most of the country in the cooler part of the growing season, but they prefer the northern tier of states for maximal yield and quality.

      Varieties

      There are more than 100 varieties of potatoes. White-skinned (actually very light brown) and red-skinned varieties with white flesh are the most common in home gardens. Some russets and yellow-fleshed types are also grown. Russet Burbank is the most important commercial variety produced in the United States, but the weather over most of the country is too warm and the moisture fluctuation too great for the production of smooth tubers and good yields. Common garden varieties offer better taste, texture and cooking quality for home use anyway.

      The following varieties are well adapted to a variety of conditions. If possible, use northern-grown seed potatoes that are certified disease free.

      Early

      • Irish Cobbler (light brown skin; often irregularly shaped)
      • Norland (red skin, smooth, resistant to scab)

      Midseason

      • Red Pontiac (red skin, deep eyes)
      • Viking (red skin, very productive)

      Late

      • Katahdin (light brown skin; smooth; resistant to some viruses, verticillium, bacterial wilts)
      • Kennebec (light brown skin, smooth; resistant to some viruses, late blight)

      Green Mountain is an old semi-rough white variety noted for its great taste. Due to a fairly high number of misshapen tubers, it has all but disappeared from commercial production. For dependable production in all seasons and the greatest-tasting baked potato ever, Green Mountain is worth the effort to find certified seed.

      Yukon Gold is the most famous of the new wave of yellow-fleshed varieties now available. Long popular in Europe, these have good flavor and moist flesh, which many people claim requires less of the fattening condiments required by dry-as-dust Russet Burbanks. Yukon Gold is a very early bearer of large, round, attractive tubers with a hint of pink around the eyes. Many grocery stores around the country now feature some name-brand version of "golden" potatoes, usually this variety. If the flavor of these market potatoes suits you, look for seed of Yukon Gold.


      When To Plant

      Potatoes are among the earliest vegetables planted in the garden. Early, midseason and late varieties all may be planted in March or early April. Planting too early in damp, cold soils makes it more likely that seed pieces rot before they can grow. Potatoes planted in March also may be frozen back to the ground by late frosts. Plants usually recover fully, but the blackened shoots are always demoralizing to the gardener. Medium-early plantings, when soils have dried and warmed, may do as well as extremely early, winter-defying plantings. Midseason and late varieties may be planted as late as the first of July. Late potatoes are best for winter storage.

      Spacing & Depth


      Potatoes are started from "seed pieces" rather than from true seed. These seed pieces may be small whole potatoes or potatoes that are cut into 1-1/2 to 2 ounce pieces. Plant the pieces soon after cutting. Be sure that there is at least one good "eye" in each seed piece. Some garden centers and seed suppliers sell "potato eyes" that weigh less than an ounce. These may be too small for optimal production. Small, whole, certified seed potatoes are often the best choice for home gardeners.

      Plant seed pieces 10 to 12 inches apart and cover in a furrow between 1 and 3 inches deep. Space rows 24 to 36 inches apart. The 24 inch spacing is often beneficial because the plants shade the soil and prevent high soil temperatures that inhibit tuber development.

      "Straw Potatoes"

      Potatoes grown by a special cultural method in that they are not hilled or cultivated after planting are called "straw potatoes." The seed pieces and rows should be spaced the same as for conventional cultivation, but the seed pieces are planted at the soil surface. Place loose straw 4 to 6 inches deep over the seed pieces and between the rows. Potato sprouts should emerge through the straw cover. Cultivation should not be necessary. Pull any weeds that manage to emerge through the straw cover and add more straw through the season if decomposition starts to thin the layer. Harvest by carefully removing the straw and picking up the tubers that lie on the soil surface. In addition to weed control, strawing has several other advantages. The straw keeps the soil temperature more uniform and about 10°F cooler, reduces water loss and results in better-shaped tubers. It is usually more rewarding to straw late varieties than early ones because there is a longer period for tuber development. Many gardeners who grow potatoes for competition in exhibits and fairs use the strawing method because the potatoes are of excellent size, color, shape and smoothness.

       

      Care

      The soil should be fertile and well drained. Clay soils should be improved with organic matter and plowed deeply in the fall. If space allows, a cover crop such as clover, buckwheat or winter rye grown in the potato bed the year before potatoes are planted improves soil structure, organic-matter content and subsequent potato production.


      Mulch is usually beneficial in growing potatoes. After the potato plants have emerged, organic mulch can be applied to conserve moisture, help keep down weeds and cool the soil. Some gardeners cover rows of early potatoes with clear plastic film at planting to warm the soil and promote early growth when the soil temperature is low. When the plants emerge, remove the film to allow the plants to grow unrestricted.

      After the potatoes break the surface of the ground, gradually build up a low ridge of loose soil by cultivation and hoeing toward the plants. This ridge, which may become 4 to 6 inches high by summer, reduces the number of "sunburned" (greened) tubers. The object of potato cultivation is to eliminate competition from weeds, to loosen and aerate the soil and to ridge the row. Misshapen potatoes develop in hard, compact soil. Use extreme caution when hoeing near potato plants because developing tubers are easily cut and ruined.

      Irrigate to assure uniform moisture while the tubers are developing. A uniform moisture supply also helps to cool the ground and eliminate knobs caused by secondary growth.

      Harvesting

      Harvest potatoes after the vines have died. Handle as gently as possible during harvest. Because the tubers develop 4 to 6 inches beneath the soil surface, a shovel or spading fork is a useful tool for digging potatoes.

      Potatoes for use in early summer ("new potatoes")may be dug before the vines die (usually in July). When the potatoes reach 1 to 2 inches in size, you may wish to dig a few hills to use for soup or to cook with creamed peas or to butter and roast.

      Late potatoes are usually dug in August or early September. They keep in the garage or basement for several weeks in their natural dormancy. Store over the winter in a dark room at a temperature between 38° and 40°F with high humidity. Check periodically for spoilage. Temperatures below 38°F cause internal damage to the tubers.

      Common Problems

      Flea beetles are shiny, usually black, beetles that often are not seen due to their small size (1/16 inch) and ability to jump quickly from plants when disturbed. They attach cabbage, Chinese cabbage, eggplant, radish, spinach, sweet corn, turnip and potato. Flea beetles scratch holes or leave white streaks in green foliage in late spring. Intense feeding results in wilting and dying of leaves and decreased yield.

      Leafhoppers are up to 3/8 inch long, green in color, and wedge-shaped. They may migrate from one area of garden to another and hop away in large numbers when foliage is disturbed. They attack bean, carrot, cucumber, Irish potato, and muskmelon. Symptoms of leafhopper damage includes curled or crinkled foliage and "hopper burn" (caused by leafhoppers' feeding, indicated by brown edges on leaves).