In Wisconsin we often don’t think about being able to get multiple crops of vegetables out of the same space in one year. With some careful planning you can grow a spring crop and a fall crop of cold-hardy vegetables.
Spring vegetables like peas, lettuce, radishes, spinach, etc. at some point will start to look sad in summer. That is an opportunity to pull those plants and replace them with some fall vegetables. The timing of this is partly dependent on the crop you are planting. You should calculate backwards from your average first fall frost the minimum expected harvest time to estimate your last opportunity to plant in the summer. Then you want to add some extra time to that number because cool temperatures slow down plant growth. Since fall frosts vary, this is not an exact science and has some art to it. To learn your first fall frost date, visit https://goo.gl/XTSi9G.
Keeping track of growing degree days/heat units and keeping a journal can help you make better planting decisions year-to-year, especially when planting for a fall harvest. To learn more about how growing degree days are calculated, visit https://goo.gl/usDKpn.
Some vegetables that are cold-hardy include broccoli, brussels sprouts, cabbage, kale, leeks, rutabaga, and turnips. Some other cold-tolerant vegetables include beets, cauliflower, celery, lettuce, peas, parsnips, and radish. Note that some of these cold-hardy vegetables have a long growing period, so wouldn’t be suitable for succession planting. For example, parsnips need to be planted in the spring as they usually take 100+ days to reach maturity.
Tools to Extend the Growing Season
Even though fall vegetables tend to be cold-hardy, protecting them from frosts can be beneficial. The issue is that the vegetables are sensitive to extreme changes in temperature. When a freeze and thaw occurs, cell walls of the plant can be damaged. Damaged leaves will look water-soaked after a thaw and will eventually turn brown. Preventing this damage will allow the vegetables to continue growing longer into the fall.
A couple of ways to protect vegetables and extend the growing season is using cold frames or floating row covers. Cold frames are made with a sturdy construction of wood plus a glass or plexiglass lid. Floating row covers are a light woven plastic or polypropylene material that allows air circulation, light, and water to get through. Floating row covers can be directly draped over crops or can be draped over a frame of PVC pipe, wood, or wire. The floating row cover is weighted down with brick, wood, or other heavy item.
You can learn more about these tools and others in the publication, “Extending the Gardening Season” at https://goo.gl/XbhZjS.
Note: This article originally was published in the Marquette County Tribune, Waushara Argus, and/or the Berlin Journal. This article was written by Lyssa Seefeldt, UW-Extension Agriculture Agent for Marquette County unless otherwise noted.