Potatoes
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Fall-planted spuds can produce outstanding yields by May. However, if you are in an area of hard Winter frosts (zones 1-7), plant potatoes in spring.
Calculating Seed Potato Quantities
One pound of potatoes plants a row approximately 8 feet long, with seed pieces spaced 8″-12″ apart. 1200 lb. per acre (600 pounds for fingerlings) is the rate for rows spaced 36″ apart, with 12″ between plants. Under most climate conditions, seed potatoes yield approximately 10-15 lbs. per pound planted, provided insects, diseases and weeds are kept under control. Days stated, for example, “80+ days”, refers to estimated days until harvest.
Preparing for Planting
Inspect your potatoes right away. If some are sprouting, handle them carefully to avoid damaging the sprouts. If you can not plant right away, store the potatoes in a dark, cool place with good humidity and ventilation.
Greening or Chitting
European market growers always pre-sprout their early potatoes for better, quicker stands and higher yields. This “greening” or “chitting” process is not necessary but it is easy to do. Just spread the potatoes in open flats, seed end up. The seed end is the end with the greatest concentration of eyes or growth buds. This area is where the strongest sprouts form. Expose the potatoes to moderate light and 60°F – 70°F for a week or two.
Preparing the seeds
Small (less than 2″) potatoes can be planted whole. Larger potatoes are cut into 1-2 ounce pieces, each containing 2 or more eyes. Dip the cut ends into dry wood ash to callous them, or spread the pieces one layer deep, away from direct sun, for a day to cure. Do not allow pieces to shrivel. Callousing is especially important if you are planting into fairly damp or cold soil.
Preparing the bed
Potatoes prefer a pH range of about 6.0-6.8 and fertile, fairly weed-free soil. They prefer sandy loam but will grow in a wide variety of soil types if the soil is well cultivated and well drained. The soil should be at least 45°F when you plant. Potatoes are not heavy feeders but do require adequate Nitrogen, Potassium, Phosphorus, Magnesium and Calcium. Home gardeners should fertilize as they would a vegetable garden. See our Spring Catalog for a full range of organic fertilizer options.
Fertilizing/Soil Amending
High quality, aerobic compost, low in wood or rice by-products, is preferable to manure as a fertilizer. If you must fertilize with manure, be sure it is well-aged and that it is incorporated shallowly into the soil at least 3-4 weeks before planting, otherwise the process of soil digestion will deprive the germinating potatoes of vital nutrients and water. Do not fertilize with fresh manure, as this can cause scab. One of the best ways to prepare the ground for potatoes is to cover crop.
Cover crops or “green manures” greatly improve the soil’s tilth, organic matter, microbial activity, and water holding capacity, and significantly increases nutrient availability for the next crop. Legume cover crops (peas, vetches, clovers, alfalfas, etc.) have the unique ability to extract Nitrogen from the air and return huge amounts of it to the soil in plant-available form. Rye, buckwheat and sweet clover mine insoluble Phosphorus from the earth and return it in plant-available form. In most areas, a Summer cover crop of cowpeas (for Nitrogen) and buckwheat (for Phosphorus) will provide an easy, and cost-effective way to prepare the ground for Fall potatoes. To prepare for Spring potatoes, many home gardeners like to Fall plant our Soil Builder Mix. For more information, see the Cover Crop section of our Fall Catalog. Wait to plant potatoes (or vegetables) for 2-4 weeks after turning under your cover crop, to allow time for it to break down in the soil.
Planting & Growing
Hoe a shallow furrow (3″ wide and 3″ deep). Gardeners can space the rows 20″ to 26″ apart, but farmers might want to make them 30″ to 36″ apart. Space potato seeds, eyes up, 12″ apart in the rows, and immediately rake 3″ of loose, fine soil over them. Do not plant any deeper than 3″.The new potatoes will grow above the seed potato, so “hilling up” is necessary to provide sufficient friable soil and to protect the new potatoes from sun exposure. About 2 weeks after planting, when the plant shoots are 4″ to 5″ high, rake a good mound of soil around them, leaving about 1″ of shoot exposed. In 2 to 3 weeks, hill again if necessary, taking care not to damage the plant’s roots. Be certain to keep the soil moist; irrigate if necessary. Mulch thickly with straw if heavy frosts are a factor.
Another approach, valued for the clean, easy dig it provides, is to grow your potatoes in straw. Do not trench, just lay the seed on the loosened soil and cover it with 6″ of straw. As sprouts appear, keep mulching with straw. You must provide enough mulch (10″ to 12″) to fully protect the new potato crop from sunlight. (Sunlight will green the potatoes, making them unfit to eat. See below.) At harvest time, just pull back the mulch.
Harvesting
Spring-planted, early varieties will be ready in about 50-60 days. For maximum freshness, dig only what you can eat in 2 days. Do not eat green potatoes, as they contain the toxic alkaloid solanine.
Later varieties, intended for Winter storage, should be “matured.” Let frost kill the vines, or kill them by scything, flaming or mowing them. Take care not to pull up the potatoes, which should stay in the ground 2 more weeks to “settle the skins.”
After harvest, store at 36°F – 40°F in dark, well-ventilated conditions. High humidity (80% – 90%) is also important. Arrange the potatoes in small piles, to improve ventilation, and cover the piles with burlap sacks, newspapers, etc. to reduce spoilage caused by condensation.
