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Potatoes (Solanum tuberosum) originated in the Andean highlands (Peru, Colombia, Ecuador, and Bolivia), where the Incas cultivated them for over 2000 years before the arrival of the Spanish in the 16th century. They were first recorded in Europe in 1587, later becoming a staple crop in Ireland and much of northern Europe. They are now widely distributed throughout the world, both for human consumption and stock feed.
Potatoes grow best in cooler temperatures (50-70 degrees F), deep, loose, well-drained, moisture retentive loam, and with adequate irrigation. Most potato varieties are adaptable, aggressive rooters, fortunately, and will produce quite respectably in less than perfect conditions. Their genetic variability is substantial. Cultivars abound for a wide range of environments and ancient Andean cultivars are currently being employed to increase the range.
In our area the worst problem is soil. Traditionally, beds are double dug and copious amounts of compost and manure are added. There are many other techniques in vogue, however, for overcoming the drainage problems of heavy clay. Try placing seed potatoes right on the soil surface and covering with straw, well rotted leaves, or compost. Or obtain a large, plastic garbage can (add drainage holes), wire cage, or other big container and plant into the lower portion (makes harvesting a breeze). If you have the means, build a raised bed. Whatever your method, as the vine grows, continue burying the stem in the chosen medium leaving about half to two thirds of the new stem exposed. This is called "hilling" and is crucial to developing large and abundant tubers (the swollen roots that you eat).
Potatoes make an easy and satisfying crop, with two pounds of seed potatoes yielding up to fifty pounds of tasty tubers. Be sure to purchase certified seed potatoes since others, including "organically" grown, can introduce diseases and be reluctant to sprout. After preparing the soil, plant whole tubers of egg size and less or cut large ones into chunks with two or more eyes (allow cuts to callus but plant before the pieces get too dry). Water enough. More water allows more and faster growth – less water produces meatier, better tasting spuds with tougher, better storing skins. (There is even evidence that low water potatoes may have a higher protein content.) Plant a few inches deep and a foot apart; generally, the more space the bigger the taters. From emergence to the end of bloom, I recommend foliar feeding about every two weeks with fish emulsion, kelp extract, etc. Additional food after blooming begins (and as tubers begin to form) is not recommended. Avoid diseases by changing the location of your potato patch at least every three years and try not to precede or follow potato plantings with other nightshade family members (tomatoes, peppers, eggplants, etc.).
Fall and winter plantings can be harvested the following April for new potatoes, in June for mature tubers. Watch the vines in June. As they start to look sickly and eventually yellow and die, it's time to dig up your crop. Whatever you manage to not eat immediately, store in the dark at 36-40 degrees F. (Light and warmth promote sprouting and/or greening.) Remember, they're still alive and need some humidity and air circulation.
Most of all, don't let stated limitations scare you. Your half shady corner might be just the spot for red, new potatoes. Your pantry is probably perfect for storage. Here in the Bay area, the profusion of microclimates may allow you to accomplish the otherwise impossible. Don't be shy, grow your own fries!
Certified Seed or Certified Organic Potatoes
Certified Seed Potatoes are potatoes that have been certified by the state in which they are grown. While not necessarily disease free, they must meet a state's standards for minimal incidence of disease. If diseases do occur, certified growers must comply with individual state programs for disease control. Certified seed is usually conventionally grown since most state requirements for disease control are not allowed by organic practices.
Certified Organic Seed Potatoes are certified by a third party accredited organization to meet the USDA's National Organic Program (NOP) regulations. They may also be certified by state, or other recognized, organic programs with even more stringent regulations.
Although seed potatoes can be both, Certified Organic Potato designations and Certified Seed Potato designations are unrelated.