Saturday, April 23, 2016

Spoke too soon...

 This week it became clear that I was wrong in describing how well the red maple flowers had weathered snow and temperatures that plunged into the twenties.  Because this week most of the female flowers have dropped from the trees, virtually ending their chance of having any kids this year. 

 April 2nd, just before the snow. 
 female red maple flowers.

 male red maple flowers.
I missed the signs of trouble on April 5th. And the
male flowers (bottom) were on their way out, anyway.

 On the 9th & 13th the flowers were blackening & shrivelling.

By the 21st so many had fallen that I wonder if any will survive at all.

Red maple’s flowering so early appears to have been a bad “decision.”  Of course, seasonal weather from year to year varies quite a bit, and so mistakes will be made—sometimes growth will begin later than is optimal for taking full advantage of the frost-free growing season, while some years—such as this one—growth will begin too early and a year of reproduction will be lost.  We can expect that the genes of these trees are optimized to split the difference between these two timing risks; that is what natural selection does. 

On the other hand, climate change is making warmer winters more common, and too-early blooming more common as well: what then?  Probably there are variations in timing among red maple trees--I know of one near my house that was weeks later in blooming than the others—and if this tree and others like it reproduce more successfully year after year, it’s more-successful, late-timing genes will spread through the red maple population: in other words, red maples will evolve to better fit the new conditions.  That, too, is what natural selection does!

The silver maples (Acer saccharinum) bloomed earlier and were farther along when the snow and freezing weather hit, and may have fared better.  Time will tell, but it looks like some developing fruit survived. 

Silver maple ice-rimed on the 3rd.

Silver maple beginning to leaf out a few days ago,
and with some maturing fruit (bottom)

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