Potatoes: Plant Your Own Successful Spuds

Potatoes are a cool season crop; they grow best in early spring and late fall when the days are warm and the nights are cool. Although the potato is a cool-season crop and the edible part of the plant is an underground stem called a tuber (not a root), the tops of the plant will not withstand frost. Potatoes need full sun for best production.

Potatoes do best in a loose, well-drained, slightly acid soil. Poorly drained soils often cause poor stands and low yields. Turn the soil 8-12 inches deep. Turn the soil over to cover all plant material. Work the soil into beds 10-12 inches high and 36 inches apart.

Amend the soil before planting with a balanced 10-20-10 feed, per 30 foot row. Some farmers like to create two ribbons or “bands” on each side of the hilled rows, and plant the seedlings in the middle. This is because no fertilizer should touch the seedlings.

Large seed potatoes for the spring crop should be cut into pieces which weigh about 1 1/2 to 2 ounces. Each seed piece must have at least one good eye. Cut the seed 5 or 6 days before planting. Hold the cut seed in a well-ventilated spot so it can heal over to prevent rotting when planted in cold, wet or very hot weather. Plants killed by a late spring frost will not come back if the seed piece is rotten. One pound of seed potatoes will make 9 to 10 seed pieces.

Potatoes have a rest period which must be broken before they will sprout. The rest period is more easily broken in small, mature potatoes. Select mature potatoes about 1 1/2 inches in diameter for fall planting. To be sure the rest period is broken, store the small seed potatoes under warm, damp conditions for 2 weeks before planting by placing them in a shady spot and covering them with moist burlap bags or mulch. The potatoes should have small sprouts at planting time.

Potatoes should be planted when the soil temperature 4 inches deep about 3 weeks before the last spring frost. If planted too early, the tops can be frozen off by spring frost. For a fall crop, plant about 110 days before the first expected frost, or mud-August in most areas.

Use a hoe or stick to open a trench about 3 inches deep down the center of the bed. Drop seed pieces 10 to 12 inches apart in the trench Step on each seed piece after dropping it to assure good contact with the soil. Cover the seed 3 inches deep. If covered too deeply, the plants will be slow to break through the soil and will be more subject to disease and seed decay.

All tubers produced on a potato plant come from above the seed piece. Since the seed piece is planted only 3 inches deep, soil must be pulled toward the plant as it grows. This allows a place for the tubers to form. Some gardeners use a thick mulch for this purpose. Tubers formed in a soft mulch often are smoother and better shaped than those grown in soil. This is especially true if the soil is heavy.

As the tubers enlarge they must be protected from sunlight. Exposure to sunlight causes them to turn green. A thick layer of mulch applied when the plants are 8 to 10 inches tall can reduce soil temperature and increase yield and quality.

The soil moisture supply should be kept constant during growth. The plant must have adequate moisture and fertilizer when the tubers are forming. This usually occurs when the plants are 6 to 8 inches tall. Apply 1 cup of fertilizer for each 30 feet of row beside the plants when they are about 4 inches tall. Water the fertilizer into the soil. This is especially important on sandy soils.

Moisture stress followed by irrigation or rainfall can cause growth cracks and second growth. If the rainfall is accompanied by hot weather, the rest period of developing tubers can be broken and can cause the tubers to sprout in the soil (see Figure 7). Too much water causes enlarged pores on tubers and makes them rot easily in storage.

Potato plants usually produce flowers and sometimes produce fruits. The fruits bear the true seed of the potato plant. They look like small tomatoes but cannot be eaten.

Potatoes are ready to harvest when the tops begin to die and the skin becomes firm on the potato. The skin is set when it does not scrape easily when rubbed with the thumb. Skin set can be speeded by cutting back the tops to the plants. Most of the potatoes should weigh 6 to 12 ounces at harvest. Harvest small, “new potatoes” during the growing season by carefully digging beside the plants with the fingers.

To harvest potatoes, dig under the plants with a shovel or spading fork. Keep the fork 8 to 10 inches away from the plant to prevent cutting the potatoes. Raise the plants and shake away the soil. Potatoes should be dug when the soil is moist. If it is too wet, the soil will stick to the potatoes. If too dry, clods will bruise the potatoes. Pull the potatoes from the vines and handle them carefully to prevent damage since damaged potatoes do not store well.

Allow the potatoes to dry, then store them in a cool spot with plenty of air movement. Most potato varieties are ready to dig 95 to 110 days after planting.

Here is a great link to growing potatoes in straw: http://www.colostate.edu/Depts/CoopExt/4DMG/VegFruit/potatoes.htm

You can treat potato seedlings with garden sulfur, prior to planting, to help reduce fungal problems. Simply place the pieces in a plastic bag containing the sulfur and shake until coated.

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