Cool season vegetables are those that can survive or prefer cool to cold air and soil temperatures. Within this group, we can break them down further. First, are those vegetables that can withstand freezing temperatures or hard frosts without damage. The second set are those vegetables that can make it through light frosts but not freezes or even a heavy frost. The latter set should be the first ones planted.
We have two more groups to go during the spring and early summer planting season. Tender vegetables cannot survive any kind of cold, including even a light frost. The last group are warm loving vegetables that absolutely require warm air and soil temperatures.
When we plant each of these groups is directly related to the hardiness zone map. For our area, that is zone 5b on the newest USDA map. The planting schedule follows what we call the "Average Frost Free Date" (AFFD), which can vary in any year by as much as two weeks!
The typical guidelines suggest those very hardy seeds and transplants can get in the ground 4 to 6 weeks ahead of that AFFD. Frost tolerant seeds and plants can be planted about 2 to 3 weeks ahead of the AFFD, but tender seeds and plants can get planted on the AFFD. The warm loving vegetables and seed wait until 1 to 2 weeks after that AFFD. For our area, the suggested AFFDs are April 15 to 25.
It is not too late for those very hardy vegetables or seeds, and we are right on time for the frost tolerant ones. Mark the calendar and plan to plant those tender and warming loving vegetables in the weeks ahead. As those very early plantings are harvested, there is the room for successive plantings that will carry harvest along. Those cold hardy vegetable transplants have been available at garden centers for a while now, and later you'll begin seeing the warming loving transplants for sale. Garden centers may even suggest waiting a bit longer before planting frost sensitive and warm loving vegetables.
By following the schedule and combining those four groups of vegetables with some successive plantings, gardeners can plant and have vegetables for the dinner table from spring through late fall. With a little effort in the fall, some late season vegetables can remain in the ground and harvested fresh through late fall into early winter. Having fresh vegetables out of your own garden with the Thanksgiving meal is something to brag about at the office.
Richard Hentschel is a Horticulture Extension Educator with University of Illinois Extension, serving DuPage, Kane and Kendall counties. Stay tuned to more garden and yard updates with "This Week in the Garden" on Facebook at facebook.com/extensiondkk/videos.