Extension Educator, Horticulture
White potatoes, also called Irish potatoes, are one of the first crops to plant in the vegetable garden. The garden adage is to plant on Good Friday, but potatoes can be planted from mid March through mid April. Tubers planted too early into cold wet soils may rot before growing.
Millionaire wannabes and horticulturists know that the part we eat is actually a tuber and not a root. Tubers are specialized underground storage stems. Tubers form when soil temperatures are between 60-70°F. Above 80°F, tuber formation stops.
There are more than 100 varieties of potatoes including early, mid-season and late varieties. The most common commercial variety is Russet Burbank, but it's not the best for home use. Caribe, Irish Cobbler, Norland and Superior are nice early varieties. Midseason varieties include Red Lasoda, Red Pontiac and the very productive Viking. Late seasons include Katahdin and Kennebec.
Green Mountain is an old variety. It does tend to have misshapen tubers, but is known for its high production and great taste. Yukon Gold is among the popular yellow-fleshed varieties. The good flavor and moist flesh is reported to require less of all those fattening condiments we slather on potatoes.
Potatoes are started from potato pieces. The "seed pieces"may be small whole potatoes or potatoes cut into 1.5 to 2 ounce pieces. Plant the pieces soon after cutting. Each seed piece should have at least one good "eye." It is best to buy certified disease-free seed potatoes rather then using the sprouting potatoes out of your potato bin. Plant seed pieces 10-12 inches apart and cover in a furrow about 2 to 3 inches deep. Space rows 24 to 36 inches apart.
After the plants emerge, form a wide ridge by hoeing soil up around the plants. By the end of summer the ridge may be 4 to 6 inches high. Ridging helps to eliminate weeds and keeps the potatoes from turning green. While the tubers are forming, be sure to provide uniform moisture. Water helps to cool the soil and eliminate the knobby tubers that bear a striking resemblance to Uncle Fred.
Harvest potatoes after the vines have died. The tubers develop four to six inches below the soil surface. New potatoes are usually dug in July. Late potatoes are usually dug in August or September. After curing, potatoes may be stored in a dark room at temperatures between 38-40°F and high humidity.
Another cultivation method, especially good for late varieties, is known as straw potatoes. The seed pieces and rows are the same as conventional cultivation, but the seed pieces are placed on top of the soil surface. Place loose straw 4 to 6 inches deep over the seed pieces and between the rows. Potato sprouts will emerge through the straw. Periodically add more straw to protect the developing tubers. At harvest time, just pull the straw back.
Whatever method is used for growing and storing potatoes, the tuber should not receive light. When potato tubers are subjected to light they will turn green and will also increase the amount of a toxic chemical called solanine.
All potatoes contain small amounts of alkaloid compounds usually just referred to as solanine. Potatoes are in the same family as the poisonous plants of belladonna and nightshade. High doses of solanine can kill. Lesser doses can cause gastrointestinal problems of nausea, diarrhea and vomiting to neurological problems of drowsiness and shortness of breath. Green potatoes could have 4 to 5 times the maximum amount of solanine considered safe. Since solanine is in the flesh, peeling does little to reduce concentrations. Green potatoes should not be eaten and should be deposited in the nearest compost pile.