2021 gardeners are reporting plant development as much as two weeks earlier than expected. Even the “early asparagus” seems earlier this year. That is a promising thought, though in the back of our minds, we can all remember those late frosts, or even a light freeze, after setting out our vegetable transplants.

Understanding the dates

The reason we want to rush spring is to get as many of those “frost free” growing days as we can. From northern Illinois to southern Illinois that can be as much as 40 days difference. So, the longer we wait to plant, the fewer growing days our vegetables get. The planting dates we hear and read about reflect the average last date of a 32-degree freeze (historical weather data). The lake effect – from Lake Michigan –allows those nearest the lake to get going as early as April 25. (Heat islands and southern exposures are influencing that as well.) Come in just a few miles from the lake and that jumps to April 30 for most of us in northeast and north central Illinois. The west and northwest portions of Cook County, Kane County, about half of DuPage County, and even parts of Kendall County are listed as May 5.

Why we plant the garden in stages

Remember, not all our vegetables will be ready for that early end of planting. Vegetables are categorized as very hardy, frost tolerant, warm season and warm loving.

• Very hardy seeds and plants can be in the garden 4 to 6 weeks before that average frost-free date and survive an actual freeze.
• Jump ahead to 2 to 3 weeks before the average frost-free date and we are a go of our frost tolerant vegetables. They can survive a light frost, but not that freeze.
• Planting those tender vegetable transplants and seeds is not advised until at (or after) that average frost-free date. If a frost is predicted, be prepared to cover the transplants and any seeds that have emerged.
• The last group of vegetable transplants and seeds are those that absolutely require warm soils and air temperatures.

Quick examples of a transplants and seed for each of the four categories are:

• Very hardy – Asparagus crowns and seeds of leaf lettuce and spinach
• Frost tolerant – Cabbage, cauliflower, and seeds of carrot and Swiss chard
• Tender – Tomato plants, and seeds of sweet corn and snap beans
• Warm loving – Pepper plants and seeds of squashes and lima bean

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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.