That magical average frost-free date of May 5 for our area is quickly approaching. Given the weather patterns we have been having, sticking to the May 5 date may not be a bad idea this year. We read about that average frost-free date where there is still a 50/50 chance of a frost and then that "absolute" frost-free date that is about two weeks later. Longtime gardeners have learned just how much they can push that average frost-free date in their landscape and vegetable garden. Conditions like the sun/shade pattern, soil types and any microclimates influence when we can begin gardening.
Garden centers have based when their woody plants, flowers and vegetables will be ready for sale based on our long-standing air and soil temperatures over many years. Right now, they are all available and ready for purchase, but that does not mean it is safe to plant all of them now in our exposed yards. Nightly, garden centers protect any of the stock that have tender foliage and expanding flower buds. Shrubs and perennials that overwintered locally and are still dormant can be planted without worry. Shrubs and perennials stocked from warmer climates can be planted knowing cold weather protection may be in order or you may hold them in a warmer location to be planted later. The same guidelines apply for the majority of perennials; still dormant, go for it. Early spring growing pansies are a common example of a flower that prefers cooler temperatures.
You can find cold and warm weather vegetable transplants now too. Those cold and cool weather transplants like cabbage, kale, and lettuces benefit from our current air and soil temperatures. Warmer season transplants, like those of tomatoes and peppers, are considered tender vegetables and do not like cooler or cold air and soil temperatures. The really warm season vegetables include our vine crops like cucumbers, watermelon, summer and winter squashes. If you were able to challenge the weather and get in the vegetable garden then potato seed pieces and a sowing of peas and lettuce has already happened.
The more you read about those very hardy, frost-tolerant, warm season and warm-loving vegetables and their planting dates, the more you will see words like "may be planted" or "may be sown up to xx days before the average freeze or frost dates." This lets us know planting and sowing dates are a bit of moving target every year. Another bit of helpful information will be how many growing days we have in a season. In northern Illinois, a good number to go with is 160 days. Compare that with the very southern part of Illinois where gardeners will have an extra 40 or so days to grow their garden vegetables.
Keep your gardening fingers crossed that our nights get slowly warmer and our daytime temperatures rise as well and plant when you can.
About the author: Richard Hentschel’s expertise extends across several subject areas with specialties in lawn care, fruit tree production, woody ornamentals, and home and community gardening. During his 45-year career in horticulture and agriculture, Hentschel became a well-known and respected expert for commercial and homeowner audiences, industry organizations, and media. He retired from University of Illinois Extension in April 2022 with nearly 30 years of service as a Horticulture Specialist and Educator in northern Illinois.