The potato (Solanum tuberosum) is one of the most important vegetable crops in the world. The edible part of the potato plant is the underground swollen stem known as a tuber. The tubers of potato cultivars vary in size, shape, color, storability, and culinary uses.
The "Irish" potato is actually a native of South America. It didn't become an important food crop in Ireland until it was introduced to the island in the sixteenth century.
Planting | Care | Harvest & Storage | Recommended Cultivars | Potential Problems | More Information
Planting
Site Preparation
Potatoes prefer loose, well-drained, fertile, slightly acid soils. Don't apply large amounts of organic matter, such as manure, to the soil where potatoes will be grown. The addition of organic matter may increase the occurrence of potato scab. The planting site should receive at least six hours of direct sun each day.
If a soil test has not been conducted, applying 1 to 2 pounds of 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.
Seed Potato Sources & Preparation
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. The 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 storing them at 60 to 70°F 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.
Planting
Potatoes should be planted as soon as the ground can be worked in the spring. This is usually early to mid-April in the central part of the state, a week earlier in southern Iowa, and a week later in northern Iowa. While there is folklore around planting potatoes on Good Friday, because the holiday moves around from year to year, planting on this holiday may put planting too early or too late.
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.
Care
Watering
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 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.
Tomato-Like Fruit
Gardeners are occasionally surprised to 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 actual fruit of the potato plant. The edible tubers are enlarged, underground stems.
Learn more in this article: Tomato-like Fruit on Potato Plants.
Harvest and Storage
Potatoes can be harvested when the tubers are small and immature or when the crop is fully mature.
New Potatoes
"New" potatoes can be dug when the tubers are more than 1 1/2 inches in diameter. The vines are still lush and green. The small, immature potatoes have thin skins and do not store well. Refrigerate new potatoes and use them within ten days.
Harvest
Potatoes grown for storage should be harvested after the vines have died and the crop is mature. Most potato cultivars mature 90-120 days after planting. To check crop maturity, dig up one or two hills after the plants have died. If the skin is thin and rubs off easily, the potatoes are not fully mature and will not store well. Allow the crop to mature in the soil for several more days before harvesting the rest of the hills. When harvesting potatoes, avoid bruising, skinning, or cutting the tubers. Damaged potatoes should be used as soon as possible.
The average yield with good management practices should be 20-30 pounds per 10-foot row.
Curing
Before storing the potatoes, cure the tubers at 50 to 60°F and high relative humidity (85 to 90 percent) for two weeks. The curing period allows minor cuts and bruises to heal. Thickening of the skin also occurs during the curing process.
Storage
Once cured, sort through the potatoes and discard any soft or shriveled tubers. These potatoes may spoil in storage and cause other potatoes to spoil. 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 50°F, the tubers will begin to sprout after 2 or 3 months. When stored below 38°F, 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 allow potatoes to freeze. Possible storage locations in the home include an extra refrigerator (set a few degrees warmer than normal), an unheated spare room, a cool basement, or an insulated garage. To increase humidity levels, store potatoes in perforated plastic bags. Do not store potatoes with apples or other fruit. Ripening fruit gives off ethylene gas, which promotes the sprouting of tubers.
Recommended Cultivars
Suggested potato cultivars for Iowa include:
- ‘Red Norland’ is an early maturing red cultivar that produces oblong, smooth potatoes with shallow eyes. They are excellent boiled or mashed but only fair when baked.
- ‘Red Gold’ is an early season cultivar with light red skin and yellow flesh. The tubers are excellent for baking and boiling.
- ‘Yukon Gold’ is an early-season yellow-fleshed cultivar. They are excellent baked, boiled, or mashed. The potatoes also store well.
- ‘Russet Norkotah’ is an early-season russet cultivar that produces blocky, oblong potatoes. It is an excellent baking potato.
- ‘Superior’ is an early to mid-season cultivar 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 cultivar that produces oblong to oval tubers with a russet skin and white flesh. Baking quality is very good.
- ‘Katahdin’ is a late maturing white cultivar that produces smooth, round, shallow-eyed tubers. They are excellent for baking.
- ‘Kennebec’ is a late maturing white cultivar with block-shaped tubers and shallow eyes. The cooking quality is excellent.
- ‘Red Pontiac’ is a late-maturing red cultivar. Potatoes are oblong with deep eyes. It produces high yields with many large tubers. Table quality is only fair. Storage quality is very good.
Potential Problems
Many diseases, disorders, and insect pests can affect potatoes during the growing season. Managing these problems is important to having a high-quality, high-yielding crop.
More information about managing potential problems found on potatoes in home gardens can be found in this article: Managing Potato Diseases, Disorders, and Pests.
More Information
- Potatoes (publication)
- Commercial Potato Production Guide (publication)
- Tomato-like Fruit on Potato Plants
- Colorado Potato Beetle Control in the Home Garden
- Vegetable Planting and Harvesting Times
- Crop Rotation in the Vegetable Garden
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