Tropical Tuber Thrives in Illinois Heat

sweet potato held in black containers
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This week’s gardening task includes planting sweet potatoes. Sweet potatoes may be a long crop (4-5 months) but with a gardener’s care, one can have poundage of storable food.

Sweet potatoes, a tropical plant, usually need four to five months of warm day and night temperatures for optimal growth. Sweet potatoes are planted in late spring when weather warms. Sweet potato slips (shoots of mature potato) are planted in loose soil.

Chris Enroth, Extension horticulture educator, explains his technique of growing his own slips. “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.”


Plant sweet potatoes into a mound of loose, loamy soil that reaches eight inches deep. Give sweet potatoes plenty of room as these vining plants prefer to spread. At a minimum, space sweet potatoes 12 inches apart and 3 feet between rows.


He describes weeding is crucial during the first few weeks of establishment. Soon 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.

Harvesting, storing

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 above ground to below ground. 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 degrees 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 degrees), dry location. Basements work well. Properly cured sweet potatoes should keep the entire winter.

Visit Chris Enroth’s blog for suggested varieties: