Zoned Out: How Climate Change Will Affect Your Gardening Choices, Part 1

| 3/12/2014 2:09:00 PM

Tags: Plant Hardiness Zones, Climate Change, Gardening, Snow Peas, Permaculture, Thermometer, St Patricks Day, temperature,

A long time I lived in Denver, Colorado, where the Italians told me that the Irish always planted their peas on St. Patrick Day. It sounded like a good idea and being a Mulligan on my Mothers side, I went along with it. It turned out those peas thought late March snows were like Manna from heaven and they flourished. Especially snow peas. Back in those days, the 1970’s, the morning temperature was below zero every day for the first two weeks of January.

Fast forward to 2012, Kansas City. It just didn’t feel right. Yes, that’s what Permaculture is teaching you; to get a feel for your environment and to observe the sky, wind, rain, and ground. I had a sneaking suspicion that it was going to be a warm spring so I started measuring the soil temperature. Peas like soil temperatures around 40 degrees Fahrenheit. Above 60 degree soil temperature the germination rate plummets.

Measuring Soil TemperaturesSoil Temperature Thermometer

I decided to record the soil temperatures with an old fashioned analog Soil Test Thermometer. In this picture soil temperature was a midsummer 80 degrees.

I took measurements as best I could 3 times a day, morning, noon, and night. I started a month before St. Patrick’s Day and immediately decided to get the peas in the ground. The measurements below show the rate of soil temperature increase over a course of a month. As can be seen, the ground was soon 20 to 25 degrees above the optimum temperature for planting peas. I had excellent germination and the best bunch of peas in years.

Soil temperature chart

Plant Hardiness Zones

Now, this little exercise, which is a good way to introduce kids to the concepts of temperature measurement, graphing, and seed germinationa all at once, got me to thinking about how fast the climate is changing. The Plant Hardiness Zone maps at The Arbor Day Foundation show the changes that occurred between 1990 and 2006. When you click the play button, you can see that the Zones seemed to have moved north 100 miles in 16 years.

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