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How to Grow Sweet Potatoes

Sweet potato harvest

Very often what grows in a garden are those fruits and vegetables we enjoy eating. Though, sometimes our gardens may exceed our appetites. After growing fifteen kale plants, my family determined, we probably could live off of two. And ten cherry tomato bushes were nine too many. One vegetable, my family does enjoy regularly is sweet potato. Baked, boiled, or fried – sweet potatoes are used more often than potatoes in my home, making it a good candidate for the garden. Let’s examine what it takes to grow sweet potatoes in our Central Illinois climate.

Sweet potato (Ipomea batatas), is a tender vegetable native to Central and South America that requires a long frost-free growing season to mature. Sweet potatoes are not true potatoes. What is harvested from the sweet potato is a tuberous root as opposed to a white potato which is a tuber.

Early spring is the time to start sweet potatoes from plants called “slips”. Order slips from a reputable seed company or make your own. Slips can be started by taking a disease-free, fully grown sweet potato from last year’s crop or the supermarket, and bury the bottom three-quarters in moist sand. In my house, we start slips by using toothpicks to suspend the sweet potatoes in a cup of water. Make sure to change the water routinely as it will turn foul after about a week. Within a couple of weeks, the sweet potato root will sprout slips, which are green shoots with exposed roots. Carefully remove the slips and plant them in the garden once all danger of frost is clear. Our family enjoys growing sweet potatoes in large containers. I’ve even grown them in hanging baskets.

If you plant sweet potatoes in the ground they should go into a mound of loose loamy soil that reaches eight-inches high. Give sweet potatoes plenty of room as these vining plants prefer to spread. At a minimum, space sweet potatoes 12-inches apart and three-feet between rows.

Little care is required once the sweet potato vines establish themselves. It can take a few weeks for the plants to establish. During this time keep on top of weeds sprouting in the garden bed. After establishment, the vines will take off in growth and ultimately cover the exposed soil in the garden bed. Where leaf nodes touch the ground, the plant sends out roots that can eventually yield more sweet potatoes. Much of my summer maintenance is redirecting sweet potato vines out of walking paths and back into the growing bed.

Ensure even irrigation; however, don’t keep the root zone constantly wet. Do not water during the last four weeks before harvest to protect the developing roots from splitting.

The biggest issue for my sweet potatoes is rodents. Voles and other small critters enjoy the taste of sweet potatoes as much as me. The best option I found is planting in containers, which provide an effective physical exclusion from these pests.

Ideally, wait until after the first frost to harvest sweet potatoes- this concentrates the sugars in the roots. Once frost hits, harvest immediately to keep any decay from spreading aboveground to belowground. If there is a long stretch of cool weather (below 55°F but above freezing) it would be a wise decision to harvest, especially if the plants show cold weather damage. Cure sweet potato roots by allowing them to dry on the ground for two to three hours, and then place in a warm room for 10 to 14 days with a temperature of 85°F and 85% relative humidity. To keep humidity high, wrap individual sweet potatoes in perforated plastic bags or newspaper. Cover the sweet potatoes with a plastic sheet or cloth. After curing, store in a cool (55°F), dry location. Basements work well. Properly cured sweet potatoes should keep the entire winter.

One sweet potato plant will yield at least two pounds. Sweet potatoes are graded based on their size. Some of the tuberous roots are bigger than my head. In my garden, this is common to have one of these large sweet potatoes per plant and commercially these massive roots get sent to processing plants to make sweet potato fries. The medium-sized roots make their way to grocery store produce aisles. You’ll undoubtedly get some small sweet potatoes. I like to call these fingerling sweet potatoes and they taste just as good as the big ones.

Sweet potatoes have many different varieties. Beauregard does well in Northern parts of the US and is the only one I’ve grown. Here are some selections to investigate for your garden:

  • Beauregard (100 days to harvest, light purple skin, dark orange flesh, extremely high yielder from Louisiana State University)
  • Bush Porto Rico (110 days, compact vines, copper skin, orange flesh, heavy yield)
  • Centennial (100 days; orange skin, flesh; good keeper; resistant to internal cork, wilt)
  • Georgia Jet (100 days, red skin, orange flesh, somewhat cold tolerant)
  • Jewell (100 days, orange flesh, good yield, excellent keeper)
  • Sumor (ivory to very light yellow flesh, may be substituted for Irish potatoes in very warm regions)
  • Vardaman (110 days, golden skin, orange flesh, compact bush type, young foliage purple)

My favorite way to prepare sweet potatoes is to bake them in a 375°F oven for 45 minutes to an hour (depending on the size). Place your sweet potato in a cast iron skillet to keep the drippings from making a mess in your oven. After baking, I cut open the potato, sprinkle a pinch of salt, and add just a drop of honey to bring out the sweet flavor.

Oh, and just so we can clear this up, sweet potato is not related to the yam, though in the marketplace the two names are often used interchangeably. The true yam, Dioscorea sp., is an entirely separate species that grows only in the tropics. Ken Johnson dives into this topic to help you settle any botanical argument. Over Thanksgiving dinner, when someone asks to, "Pass the yams," you'll be ready. Check his article here What's the Difference Between Sweet Potatoes and Yams?


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