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.
From Lisa Johnson, Dane County UWEX Horticulture Educator
Teaching Garden Please visit http://dane.uwex.edu/horticulture/teaching-garden/ to see a map of the garden, visit links to our plant list (with photos) and see a short video of last year’s color wheel garden. I recorded some short videos last week at our work day that I hope to upload soon. Remember our plant sale is coming up Sunday May 21 11 am-3 pm. We are still taking donations—the protocol for donating plants, especially as related to screening for jumping worms (we don’t want any of those!!) appears later in the newsletter. Of course, you cannot donate if you suspect or know that you have them.
Programming Potpourri: We have just finished the annual Green Thumb Gardening Series, and as with every year I feel so blessed to have our talented UWEX specialists and other amazing professionals like Frank Hassler from Good Oak Ecological Services on hand to give such great presentations! I gave 4 of the 9 presentations this time around, including a new topic on berries. This year we also had translators for Spanish-speaking participants, which was a nice addition.
Hort Short: I am devoting this section to a report on jumping worms. I think people are already aware of the basic effects that jumping worms have on changing the structure and nutritional content of the soil so that it is hard for plants and especially seedlings to thrive. When I hear that wild ginger, a pretty aggressive native plant has troubles in an infested soil, I know the situation is serious. We have infestations that I know of in Middleton, Maple Bluff, the Arboretum and surrounding properties, Olbrich and some surroundings, East side (including my garden), West side, and Shorewood. I am sure there are a number of folks who don’t know they have the as well. I am not advising people to use any free compost that has not been produced following DNR guidelines. Only purchase compost created by licensed companies complying with the DNR’s NR 502.12 which large ones like Purple Cow definitely are. See info at these two links: http://dnr.wi.gov/files/PDF/pubs/wa/WA1585.pdf and
The first link is: Temperature Monitoring at Licensed Compost Facilities which lays out the requirements. Under NR 502.12 the compost piles are required to hold a temperature of 131 degrees for 15 days and the windrows/piles must be turned 5 times to ensure even distribution of temps and companies are required to keep books logging the process since they can be inspected by the DNR at any time. However, even this is no guarantee, since the cocoons are so small and it is possible that some could be at the edge of a pile and not get thoroughly heated. Jumping worms have already hatched this year (April 23 observation) and are about an inch long. They are hard to ID now since their clitellum is so small, but they still exhibit the jumping behavior. Adult jumping worms usually are not seen until late June. Their life cycle lasts 60 days so with this early hatch, definitely two or even three generations can be produced per year. The jumping worm is especially destructive since it lives right in the duff layer rather than lower in the soil profile. Jumping worms tend to outcompete European earthworms to become the only species in forest environments. They consume the layer of leaves and other organic matter on top of the soil faster than other earthworm species. They have been found in Dane, Sheboygan, Jefferson, Waukesha, Milwaukee and Racine counties, and signs of the worms (though no adults) have been noted in 8 other counties. Jumping worms have also been found in some states in the Eastern U.S. We don’t know how long they have been here in Wisconsin, but introduction through contaminated soils or plants is suspected. Since they can spread very quickly, it is important to slow the spread. Best management practices are being developed by the DNR and municipalities. Don’t share plant divisions from your garden or soil if you know you have jumping worms. I’ve included a photo (from my yard!) of an adult worm.
Jumping worms are parthenogenetic, producing eggs without the need for a mate, so just one worm can start a new population. Their eggs survive as microscopic cocoons over winter, with all the adults dying in fall. Look now for the ‘soil signature’ from their feeding during the previous season. Jumping worms feed on soil organic matter, leaf litter and mulch and create very grainy-looking and hard little pellets when they excrete. The excretions resemble coffee grounds, and have poor structure for plants to grow in. Also, the worms’ feeding removes the organic matter that plants, fungi and bacteria need for nutrients. Adult jumping worms are 3 to 5 inches long but can grow to up to 7 inches in length. Jumping worms resemble regular earthworms but there are some important differences. Unlike European earthworms, they don’t produce slime and are more gray or brown in color than pink. Their clitellum, the band of lighter-colored tissue near the head, is smooth, not raised like other earthworms and whitish, not pink. It also goes all the way around the body, not just partway, like the European worms. The body is more rigid as well. Jumping worms get their name from their behavior—when handled, they thrash violently, may jump into the air or even shed their tails. They move in a serpentine fashion like snakes, as well. Unfortunately, other than killing any worms you find by placing them in a closed plastic bag in the sun, there are no products labeled to kill them. There is a concern that soil drenches would also kill beneficial soil organisms. There is some research using biochar that shows promise, and there is a product being tested at the Arboretum and Olbrich gardens, but again there is concern that soil microbes would be affected as well as other worm species. To report a finding of jumping worms, email Invasive.Species@wi.gov . For more information and to see more photos, visit http://dnr.wi.gov/ and search for the keyword ‘jumping worm’.