Sweet Potatoes (Ipomoea batatas) are starchy root vegetables originating from Central or South America.
Not to be confused with starchier and drier yams (Dioscorea) from Africa and Asia, sweet potatoes have a long shelf life and are usually sweeter and moister than regular white potatoes (Solanum tuberosum). In addition to being delicious, they are a very important crop in diet planning, because of the number of calories they contain per pound, and for overall sustainable gardening and farming!
Globally, people get many calories through growing and eating both “Irish” potatoes and sweet potatoes as staple crops. Sweet potatoes are the most practical calorie producing root crop by weight (see HTGMV 9th ed., p. 40 for more details). Garlic is more weight-efficient, but one can generally eat only 2 to 3 cloves daily, while 5 pounds of sweet potatoes—an amount that can reasonably be consumed by an adult human—can provide all the required calories to sustain a person for a day. Of course, you will need to eat other crops to get the essential amino acids, vitamins and minerals you need, but if you start with sweet potatoes as the base of your food pyramid, you’ll be on solid ground. (Also, using other crops for the missing nutrients noted above will allow you to reduce the weight of sweet potatoes you need to eat. This is because those other crops also contain calories.)
Sweet potatoes come in many colors—white, yellow, red and even purple. Purple ones are an ancient superfood and turn a beautiful bright violet color when cooked! They are high in anthocyanins, the antioxidant compounds that have been linked with a reduced cancer risk. The Stokes Purple variety is available from friedas.com/stokes-purple-sweet-potato, and the Hawaiian Purple variety is available at hawaiiveggiefarm.com. Check out this Pinterest board on purple sweet potatoes! https://bit.ly/2IWc440
Most sweet potato varieties take 6-8 months to mature. This makes it difficult to grow in many temperate climates, unless you do it under a double-walled miniature greenhouse (see HTGMV 9th ed., pp. 205-212. A plus for 6- to 8-month maturing varieties is the fact that you can harvest up to 20% of the nutrient-rich leaves (known as talbos ng camote or kamote tops in Spanish-speaking countries) for eating in the second month without lessening the ultimate yield. Excitingly, Sand Hill Preservation Center in Iowa, carries 225 sweet potato varieties, (including Korean Purple), including eight certified organic sweet potato varieties that mature in only three months–and they come in many colors!
A good article on the Purple Sweet Potato can be found in the spring 2018 issue of Heirloom Gardener. Another key resource for short growing season growing is Sweet Potatoes for the Home Garden—with Special Techniques for Northern Growers, by Ken Allan (available only from Mapple Farm).
Humans aren’t the only ones who love these delicious tubers: amazingly, gophers know three days before the optimal harvesting point that it is time to eat! To eliminate or minimize this challenge, you can build underground protection with a gopher cage (see “New Gopher Cage” article and illustrative photos on pp. 2-3 in the May, 2007 Ecology Action Newsletter).
For a Biointensive garden, sweet potato starts and slips should be planted on 9-inch offset centers, 6 inches deep. For full sweet potato planning information see the Master Charts in HTGMV 9th ed., pp. 150-151.
Hungry? Get planting!
(images from hawaiiveggiefarm.com, mother earth news, http://www.heirloomgardener.com and http://www.southernexposure.com)