One of the most popular vegetables in the home garden is the "Irish" potato. A native of South America, the potato didn't become an important food crop until it was introduced to Ireland in the sixteenth century.
Potatoes prefer loose, fertile, slightly acid soils. Don't apply large amounts of organic matter, such as manure, to the soil where potatoes are to be grown. The addition of organic matter may increase the occurrence of potato scab. If a soil test has not been conducted, an application of 1 to 2 pounds of an all-purpose garden fertilizer, such as 10-10-10, per 100 square feet should be adequate for most home gardens. Broadcast and incorporate the fertilizer shortly before planting.
Since potatoes are susceptible to several serious diseases, buy certified disease-free potatoes from a reliable garden center or nursery. Home-grown potatoes saved from the previous year's crop may carry undetectable diseases. Potatoes purchased at supermarkets may have been treated to prevent sprouting. Best results (excellent quality and high yields) are obtained with certified seed potatoes.
Large potatoes should be cut into sections or pieces, each containing 1 or 2 "eyes" or buds. Small potatoes may be planted whole. Seed piece decay may be a problem in cool, wet soils. This problem may be prevented by treating the cut seed pieces with a fungicide or by storing them at a temperature of 60 to 70F and 85% relative humidity for several days. These storage conditions allow the cut surfaces of the seed pieces to heal or callus over before they are planted.
Potatoes should be planted as soon as the ground can be worked in the spring. This is usually early April in the central part of the state, a week earlier in southern Iowa and a week later in northern Iowa. Set seed pieces, cut side down, and small whole potatoes about 1 foot apart in a furrow 4 inches deep. Rows should be spaced 2 to 3 feet apart.
Suggested potato varieties for Iowa include:
- Red Norland is an early maturing red variety that produces oblong, smooth potatoes with shallow eyes. They are excellent boiled or mashed, but are only fair when baked.
- Russet Norkotah is an early season russet variety that produces blocky, oblong potatoes. It is an excellent baking potato.
- Yukon Gold is an early season yellow-fleshed variety. They are excellent baked, boiled, or mashed. The potatoes also store well.
- Superior is an early to mid-season variety with round to oblong tubers and medium deep eyes. The potatoes are very good baked, boiled, or mashed. It is resistant to scab.
- Goldrush is a mid-season variety that produces oblong to oval tubers with a russet skin and white flesh. Baking quality is very good.
- Katahdin is a late maturing white variety that produces smooth, round, shallow-eyed tubers. Excellent for baking.
- Kennebec is a late maturing white variety with block-shaped tubers and shallow eyes. Cooking quality is excellent.
- Red Pontiac is a late maturing red variety. Potatoes are oblong with deep eyes. It produces high yields with many large tubers. Table quality is only fair. Storage quality is very good.
- While the standard potato varieties listed above perform well in Iowa, there are many other varieties with unusual colors and shapes. These heirloom and novelty varieties are tasty and fun additions to the garden. Some heirloom or novelty varieties of interest include:
- Cranberry Red is a mid-season variety that produces large tubers with a red skin and pale pink flesh.
- All Blue is a mid to late season variety with deep blue skin and blue flesh. The medium-sized tubers are good mashed and in salads. Stores well.
- Yellow Finn is a mid to late season variety that produces oblong, medium-sized tubers with light tan skin and yellow flesh. Good for salads.
- German Butterball is a late maturing variety with golden yellow skin and yellow flesh.
- Russian Banana is a late maturing variety that produces small, banana-shaped tubers. Skin and flesh are yellow. Excellent in salads.
Like most other vegetables, potatoes require 1 inch of water per week during the growing season. This is especially true during tuber development which typically begins in early to mid-June. Best yields are obtained when plants have a uniform, consistent supply of moisture during tuber development. Water deeply once a week in dry weather. Alternating wet and dry periods during tuber development can cause hollow heart, growth cracks, and knobs.
Weed Control and Hilling
Control weeds by pulling and hoeing. Cultivation should be shallow (2 inches or less) to avoid damaging the potato plant s roots or tubers. When hoeing, pull or mound soil around the bases of the plants. "Hilling" provides loose soil for the developing tubers. It also prevents the greening (due to exposure to sunlight) of shallow tubers.
Occasionally, gardeners will find small, round, green, tomato-like fruit on their potato plants. These fruit are not the result of cross-pollination with tomatoes. They are the true fruit of the potato plant. Most potato flowers dry up and fall off the plants without setting fruit. However, a few flowers will develop into fruit. The potato fruit are of no value to the gardener. The tomato-like fruit are not edible. Also, potatoes don t come true from seed. The variety 'Yukon Gold' sets fruit more heavily than most varieties.
Harvest and Storage
"New" potatoes can be dug when the tubers are more than 1 1/2 inches in diameter. New potatoes should be used immediately as they do not store well.
Potatoes grown for storage should be harvested after the vines have died and the crop is mature. When harvesting potatoes, avoid bruising, skinning, or cutting the tubers. Damaged potatoes should be used as soon as possible.
Before placing the potatoes in storage, cure the tubers at a temperature of 50 to 60F and high relative humidity (85 to 90 percent) for 2 weeks. The curing period allows minor cuts and bruises to heal. Thickening of the skin also occurs during the curing process.
Once cured, store potatoes at a temperature of 40 F and relative humidity of 90 percent. Store in a dark location as potatoes turn green when exposed to light. If storage temperatures are above 50F, the tubers will begin to sprout after 2 or 3 months. When stored below 40EF, potatoes develop a sugary, sweet taste. Sugary potatoes can be restored to their natural flavor by placing them at room temperature for a few days prior to use. Do not store potatoes with apples or other fruit. Ripening fruit give off ethylene gas which promotes sprouting of tubers.
This article originally appeared in the March 8, 2002 issue, pp. 22-23.