Potatoes hilled and mulched with straw to avoid sunburn and decrease weeds. Courtesy: David Graper
Potatoes can be relatively easy to grow, especially if they are started from seed potatoes that are certified disease-free. Potatoes can be grown in a variety of set-ups, ranging from traditional rows in the garden to seed tubers placed on top of the ground and covered with straw, to straw bales, to “grow bags” of water-permeable plastic, to garbage cans or tires in which straw is piled up. The goal is to provide the plants with good conditions to form tubers, while making the eventual harvest of those tubers easier. As the tubers begin to form, soil (or straw) is added to the base of the plant to keep developing tubers from being exposed to the light, which can turn them green and inedible.
Long nights (i.e. short days) encourage tuber formation, especially in longer-season varieties. The tubers start to form about the same time as the plants flower (four to six weeks after planting), but flowering is not required for the tubers to form – that’s just coincidence. Sometimes the flowers will set seed in a fruit that looks very much like a miniature tomato, but is not edible.
Although potatoes are relatively easy to grow, they are also very responsive to their environment, which can lead to problems. If the soil temperatures are too high (over 80 degrees F), the tubers may not grow, or even shrink and be re-absorbed back into the plant, or they may become knobby.
Although potatoes require steady moisture throughout the tuber-forming period to avoid growth cracks or knobs, they are also sensitive to too much moisture, so the ideal soil or growing medium is well-drained. Too much nitrogen can delay tuber formation as the plant puts all its energy into growing leaves.
Potato scab (corky patches on the tuber skin) can be a problem in our high pH soils, especially if manures have been used for fertilizing. Although scab-infected potatoes are perfectly safe to eat after peeling, the problem can be decreased by planting varieties that have some resistance, such as “Norland”, “Russet Burbank” (or most other Russet potatoes), “Gold Rush”, “Superior”, “Red Gold”, or “Norchip”. A white variety called “Dakota Pearl” and the Russet “Gold Rush” are two of the most resistant varieties. “Red Pontiac” and “Yukon Gold” are unfortunately very susceptible to this disease.
How and when the tubers are harvested, and how they are stored will determine how long they will stay good to eat. Potatoes harvested when the vines are still green (i.e., “new” potatoes) will have thin skins, and will not keep for long periods of time. If the tubers are harvested 10 to 14 days after the tops have died down, they will develop stronger thicker skins that facilitate long-term storage. Commercially, chemicals may be used to kill the tops. Home gardeners can wait for frost, break the tops, or pull the plants just enough to break some of the roots in order to get the tops to die back. Holding the harvested potatoes in the dark at 60 to 70 degrees F in high humidity for 4 or 5 days can help cure the skins. Damp cloths or sand can be used to raise the humidity, but the potatoes should not touch wet surfaces. Longer-term storage should also be in the dark, preferably at temperatures between 40 and 50 degrees, again with humidity but not wet.
A medium sized potato has just 100 calories with no fat (it’s the butter that we put on them that can be fattening!), with 4 grams of high-quality protein and 45% of an adult’s RDA of Vitamin C.