Extension Express for June 2017

The Dane County Sweet Potato Project is off to another productive season. The goal is to increase healthy food access in Dane County by growing sweet potatoes for local food pantries. Dane County UW-Extension does this by teaching community members how to grow sweet potatoes and provides free sweet potato slips, or transplants to community members. Since 2014, local growers have donated over 13,000 pounds! Sweet potatoes are a great choice for this project because they are a very nutrient dense vegetable, if properly cured, can last up to a year without refrigeration, making them ideal for food pantries.

Growing sweet potatoes can be challenging in Zone 5, but with the right soil preparation and management, they can be a very productive and enjoyable vegetable to grow. Here is some information on how to grow them.

Sweet potatoes are propagated vegetatively rather than by seeds. The saved sweet potato is used to produce slips, or transplants. They can be planted in late May through mid June in Wisconsin when soil temperatures are 70 to 80 degrees and all danger of frost has passed. In zone 5, Beauregard and Georgia Jet varieties do well as they have been selected for a shorter growing season and cold hardiness. When planting, remove all the petioles off the slip and plant the empty nodes in under the soil. A node is a bump or swelling on the slip where a leaf was attached. Each node will form its own sweet potato! Make sure that there is good soil moisture and water every other day for 1-2 weeks after transplanting as the slips are still fragile and developing roots during this period. The spacing should be about 18 inches in rows or 3x3 feet for square foot gardening. The wider the spacing between plants, the faster the sweet potatoes grow. Sweet potatoes can tolerate acidic soils, but plant in raised hills or windrows if your soil is more clay-based. Raised beds aid in root development and improve soil drainage and aeration as sweet potatoes do not tolerate waterlogged soils. Control weeds around the potato until the sweet potato vines cover the by mulching around the plants with newspaper and hay. Black plastic sheet mulch can also be used and is great for bringing the soil temperature up as sweet potatoes love hot soil and are very drought tolerant. After 90-100 days have passed, you may start harvesting by using a tine or pitch fork. Be sure to harvest before the first fall frost as dying vines may start to rot the potato roots. Be careful when harvesting as the potato skin is very fragile before the being cured. The potato can be eaten immediately, but will firm up for storage after being cured in a hot (90+ degrees and humid environment for 1-2 weeks.