Considered an exotic holiday root vegetable in many parts of the country, sweet potatoes are often relegated to the grade-school science project that involves a chunk of tuber and a jar of water. Perhaps because those experiments mainly produce long vines and fibrous roots, and the vegetation looks slightly tropical, one might conclude that it just isn’t possible to grow sweet potatoes anywhere but in the Deep South. Nothing could be further from reality.
Years after an enlightening fall visit to the Benton Harbor market, where I first discovered Michigan-grown sweet potatoes, I decided to investigate raising the crop for my family’s produce business, Magicland Farms, a roadside farmers’ market in west-central Michigan where we only sell what we grow. After considerable research, I decided to make a test planting of sweet potatoes to find out if it was possible to make money raising and selling the crop. I then placed orders for Beauregard and Georgia Jet sweet potato slips and planted them in raised beds. Here are the highlights of my test planting:
Mid-May – Planted sweet potato slips 12 to 15 inches apart, through black plastic with trickle irrigation.
Late May – Late, light frost killed a few plants, but most were just set back – the part of the slip below the plastic was OK.
June through mid-August – Twice weeded rows between raised beds. Turned on water to drip tape for a few days when soil beneath plastic got dry. Also applied soluble fertilizer through drip tape three times.
Mid-August through mid-September – Stopped watering. Sweet potato vines covered plastic.
September 23 – Dug a few plants – it was obvious from the size and quantity that growing sweet potatoes in Michigan is feasible.
October 1 – First frost of the season killed some of the top growth on the sweet potato vines.
October 8 – Average soil temperature dipped to near 60 degrees. Hand dug all remaining vines. Some plants were loaded with big sweet potatoes while others nearby produced fewer and smaller tubers.
The Michigan summer of 2009 was one of the coolest and wettest in most people’s memory. Despite this, my test planting showed that it may be profitable to grow sweet potatoes in Michigan for local markets. If you want a good crop of sweet potatoes, make sure the vines are growing vigorously by the Fourth of July.
- If you use peat pots, remove bottom and one or more sides of the pots before planting in garden.
- Freshly dug sweet potatoes aren’t exceptionally sweet. However, a month later, they are nice and sweet and continue to slowly sweeten.
- Sweet potatoes should be cured so they keep better. (See Page 54.)
- In general, sweet potato plants are easy to grow in the North. The trick is to get the plants growing vigorously early so they form good-sized sweet potatoes. Start with as large a plant as possible.
- When ordering slips, try to obtain them about two weeks BEFORE your average last frost date and start them in pots placed in a cold frame or under fluorescent lights.
- Move vigorous plants to the garden when you would tomatoes – soil temperature at least 60 degrees – and cover when the threat of frost is real.
When Magicland Farms closes its doors in late fall, Tom Fox pursues his other interests, including writing on a variety of topics and designing useful and intriguing electronic gadgets.