I've heard it on the news, in conversation, and social media, "This warm late fall weather sure is great! I hope the entire winter is like this!"
Is this weather great? Of course! Last weekend I took my kids out to Dickens on the Square, a pleasant downtown event in Macomb. In years past, we are bundled up, freezing as we walk from activity to activity. This year, 2017, Dickens on the Square was jacket weather. As I write, the temperature in Macomb is 63 degrees Fahrenheit on December 4. By the time you read this, our weather will return to levels that are more seasonal. Already I see the wind has picked up, blowing in a chilly breeze from the north.
But the statement remains in my head, "I hope the entire winter is like this!" That statement begs the question, what if the weather stayed warm the entire winter. Let's go down this hypothetical thought path.
What would happen if our Midwestern winter was more akin to spring or fall weather? First thing, our soils would not freeze. As soil freezes and thaws it expands and contracts, breaking large clods into smaller pieces, naturally moving soil and its many components (organic matter, nutrients, micro and macro organisms, etc.) through the top inches of soil horizon. Many farmers and gardeners rely on the freeze/thaw of winter to break up tilled land to create a soil surface more conducive to seeding next spring. Without the freeze/thaw cycle of winter, tilled gardens and fields would retain their large soil clods.
The freeze/thaw effect is also a component of the germination process of many native prairie seeds. A combination of expanding and contracting soils and exposure to cold temperatures is what many native prairie seeds require to break dormancy.
Insect populations also are boosted by warm winter temperatures. However, our native insects are adapted to the warmest and coldest winters the Midwest can throw at them. Even though a lot of the bad insects survive, so do the predators of those pests. When it comes to our native insects, it equals out.
The problem lies in the non-native pests that have no natural predators and plagued our landscapes in recent years. Consider the Japanese beetle. Japanese beetles, while thriving mid-summer, are from a milder location in Asia. In their grub stage, Japanese beetles will tunnel down lower in the soil profile to escape the freezing soil. Fortunately, they can only travel so far in the soil. According to retired Extension entomologist, Phil Nixon, "Research has shown that Japanese beetle grubs do not migrate deeper than 11 inches into the soil for the winter. They die if the soil temperature reaches 15 degrees F or if they are subjected to freezing temperatures for two months."
Mild winter weather will also signal many of our pollinators to emerge and begin foraging. Even with the warm temperatures, there will be no flowering plants due to the short days of winter. A mild winter will place again another stress on our native pollinators, hastening their decline into extinction.
Many plants also have specific chilling requirements (under 45 degrees F) to break dormancy and initiate flowering, fruiting, and leaf emergence. If you grow fruit or nut trees, a mild winter means you will not meet your chilling requirement. As an example, on average most varieties of apple trees require over 1,200 chilling hours. What's more, fluctuating temperatures from warm to cold increases the number of chilling hours. If an apple tree doesn't get that 1,200 minimum of chilling hours, fruit development is hampered and causes a significant impact on commercial and backyard orchard growers across the state.
Before you tell me, "This warm late fall weather sure is great! I hope the entire winter is like this!" please think about what you just read. Mentioned prior is just the tip of the melting iceberg. If it is warm winter weather you desire, I hear Arizona is lovely this time of year.