Friday, March 27, 2009

Time Machine

They say that spring moves north at about 15 miles per day. In other words, all other things being equal, a flower that first blooms here today will first bloom tomorrow in a town 15 miles north of here; or, to bring it closer to reality… the elm trees that were starting to flower Wednesday evening in the Whole Foods parking lot (Northbrook) should flower here today. And indeed, the buds, which have been swollen for a few days, have opened up (see photo, taken this morning). When you touch them, a cloud of pollen flies into the air.

This equation only works, of course, with the “all things being equal” part, and that’s a tall order. Same light conditions, soil conditions, watering conditions… But on average, it works out; aerial photographs taken weekly will show green moving northward in hundred mile increments. (100 miles a week = about 15 miles a day. Perhaps I didn’t need to spell that out for my loyal readers, but please remember that my normal audience is in the 10-year-old range.)

This means that, in the next week, as we travel to North Carolina and back, covering about 450 miles in north-south-ness, we will be phenologically transported 30 days into the future, and back again. It will be green when we get there! That’s a lot of time travel in a five-day trip!

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