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Secrets for Growing Sweet Potatoes

Can we grow sweet potatoes in North Dakota? Absolutely!

Sweet potato
Sweet potato after one year in storage
Can you grow quality sweet potatoes in North Dakota? Sweet potatoes are from the tropics. They like a hot, long growing season and we have one of the coldest, shortest growing seasons in the USA. Most sweet potato roots grown in North Dakota are scrawny and yields are low.

There’s hope. The family of Corey and Jessica Silvernagel from Lincoln, North Dakota (Corey Silvernagel with his son Mason.) has proven you can grow good crops of quality roots in our state.

They start by growing their own slips (sprouts). In mid to late March, they take sweet potatoes from the grocery store, cut them in half and place the cut ends in water. Many of us have done this as kids for school projects (Sweet potato sprouts - thumbnail). Once a plant develops into a 4-inch slip, they break it off and put it into a glass of water (3/4 inch deep) to form more roots. New slips can alternatively be set in potting soil to grow more roots (Sweet potato slip). 

In mid to late May, they set out the slips. The slips are placed into small mounds spaced 4–5 feet in both directions. They spread the roots out when planting and set each slip so its crown is 1 inch deep.

Once the temps warm up, the vines sprawl over the garden like a rich green carpet. The Silvernagels applied sheep manure to their garden this spring, but otherwise they do not fertilize the plants.

Sweet potatoes require a long growing season and the family protects the vines from light frosts by covering them with blankets. Harvest commences after a hard frost. 

Harvested roots (8 pounds per plant) are cured near the furnace and stored in the basement. They showed me roots from last year’s harvest and the roots were still firm and just beginning to sprout (photo at top right).

The secret seems to be growing your own slips. Their slips have healthy root systems and never suffered shock before being set in the garden. In contrast, slips purchased from garden centers and seed companies obviously suffer significant stress when dug, cooled and later transported across the country.

Can we grow quality sweet potatoes in North Dakota? Absolutely! Seeing is believing.

Written by Tom Kalb, Extension Horticulturist, North Dakota State University. Published in the NDSU Yard & Garden Report, August 31, 2016. Photos were made available under a Creative Commons licenses specified by the photographers: Tom Kalb, NDSU; Colleen and Sat Garcia; and Cristina Santiestevan, http://outlawgarden.com.

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