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Down the Garden Path

What's up with the Weather?

If plants could think, they probably are wondering, "What is going on? Why am I trying to grow in such difficult and changing weather conditions?" I am sure migratory birds and other wildlife are wondering the same thing.

There are groups and organizations that monitor just about everything these days, and right now the National Phenology Network (NPN) has been very busy very early in 2017 tracking plants as they begin to leaf out. Tracking for Illinois shows we are as much as 20 days ahead of what we know as "normal" for central through southern Illinois. Locally, we are between 15 and 20 days ahead. Silver maples typically begin blooming around March 1, and this year bud swell and bloom began mid-February. NPN monitors things like crocus showing above the soil, trees and shrubs showing "green tip," and other weather conditions signaling spring.

NPN maps show the earliest spring we have had recently was 2012. I remember the drought that summer, but not the early spring. One of their maps show that in 2012, spring showed up early even in northern Illinois. 2017 so far shows an early spring as well.

One of the ways we track plant progress is collecting data on growing degree days (GDD). There are a couple of models used, one based on 32 degrees and the other based on 50 degrees. These models used to track insect development during the growing season as well.

GDD data for much of the Midwest, including our area, reports a similar trend to the tracking data for plants leafing out. The more GDDs ahead of normal, the more plant development happens. We are several hundred GDDs ahead of normal right now, and that can change yard and garden decisions. For example, it may influence timing for crabgrass prevention applications by the lawn care industry.

In the home landscape, gardeners are witnessing early spring in that microenvironment that exists as your yard. Spring bulbs are more developed in a southern exposure than a northern one. Peach trees run the risk of having their blooms killed by a late frost or freeze in a normal spring, and the risk is higher this year. Early spring bulbs have already been up and blooming.

One caution this spring will be deciding when to set out your vegetable transplants based on their preferences for air and soil temperatures. Tomatoes can go out before the peppers and vine crop transplants that do not tolerate even cool weather, so both the soil and air temperatures need to be warm. Greenhouses and garden centers sow those seeds based on a normal year, so while they are available for sale, it does not necessarily translate into "time to plant." Go ahead and make your purchases, but hold off on planting the garden until conditions are right. Tomatoes, peppers and vine crops planted too early will be slow to establish, flower and fruit.

Here's a general outline of soil temperatures needed for planting various crops:

Need Cool Soil (50° - 65º F)

Celery Onion

Spinach Lettuce

Peas Turnip



Tolerate Cool Soil (50º - 85º F)

Chard Mustard Brussels sprouts

Kohlrabi Broccoli Beet

Carrot Kohlrabi Broccoli

Swiss Chard Mustard Collards

Parsley Cabbage Endive

Parsnip Cauliflower Kale



Need Warm Soil (65º - 85º F)

Beans Muskmelon

Squash Corn

Okra Tomato

Cucumber Peanut

Watermelon Pepper

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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