Q: Is it possible to grow traditional southern crops such as sweet potatoes and okra in Wisconsin’s shorter, cooler growing season?
—Blair Dexter, Eau Claire, Wisconsin
A: “Yes!” says Patti Nagai, Ph.D., Racine County University of Wisconsin horticulture educator. “I have grown okra and sweet potatoes here in Wisconsin.” Nagai trains and guides master gardeners in Wisconsin, but she credits her horticultural roots in Mississippi for giving her a fondness for southern types and varieties of vegetables.
The key to selecting southern plants for northern climates is to look at the number of days to harvest, Nagai explains. “Okra is not much of a problem, because there are many cultivars that produce in less than 65 or 70 days. There is a cultivar called ‘Baby Bubba’ that produces fruit between 50 and 60 days, and because it is a dwarf plant, it can be grown in containers. We grew it a few years ago, but it didn’t produce as well as ‘Burgundy’ and ‘Clemson Spineless’, both of which produce in about 60 days and get to be about 61⁄2 feet tall.” Okra plants have gorgeous flowers, Nagai enthuses. “The ‘Burgundy’ okra would make a beautiful back-border plant in a flowerbed.”
Heat-loving sweet potatoes present more of a challenge for northern gardeners. “Sweet potatoes, even ‘Beauregard’, are still long-season,” Nagai says, noting that even the earliest-maturing cultivars need 90 to 100 days. “If planted soon enough, they will produce well in the southern half of Wisconsin.” They prefer loose or sandy soil. In clay or rocky soil, the storage roots will be malformed. Sweet potatoes appreciate uniform moisture and do extremely well in raised beds or large containers filled with a compost-based soil mixture. “This is how we grow them in the community garden, because our native soils tend to be both clayey and rocky,” she says.
“In the center sands region of Wisconsin, sweet potatoes are grown commercially for the frozen sweet potato fries industry,” Nagai adds. “So it is not only possible for home gardens; it is commercially viable.”
When timing your crops, be sure to leave enough time to enjoy the fruits of your labors, says Nagai. “With okra, ‘days to harvest’ is the days it takes from seed to first fruit, but your actual harvest will last from first fruit to frost. To get a reasonable amount of okra, it would be great to have at least 30 days of harvest time, so it puts it on a comparable basis with the sweet potato. A 90-day sweet potato means from the time you plant the ‘slips’ (little plantlets grown from the previous year’s storage roots) to the time you dig the plant, so the harvest is all at once,” she continues. “If both [okra and sweet potatoes] are planted June 1 in warm soil, each crop would need 3 months to produce a decent harvest. But that only puts you at September 1, and most of Wisconsin is still frost-free September 1. Both crops will continue to grow until frost.”
Ask Organic Gardening is edited by Deb Martin
Originally published in Organic Gardening magazine, April/May 2014