Monday, October 12, 2015

Subtle Colors

"Peak color" in the fall is a thing to glory in.  I have already seen announcements for tours up north to view peak color at these higher latitudes where it comes earlier, and it will be here soon enough.  But the more subtle color at this time of the season has charms of its own.  Here are a few trees to look for right now.

Sugar maples have been turning by ones and twos for quite a while.  Sadly, many of these lose their leaves even as they turn, so that you'll notice more color on the ground than in the sparse crowns above.  (Those that hold their leaves will often finally reach a brilliant flame orange that is truly breath-taking.)

Precocious show-off, September 12th.

Trees turn individually, and even by parts.  Early October.

Sugar maple leaves often fall immediately after they turn.

Foretaste of the color to come.

Red maples have been sidling (edging) into the season, first with red leaf-stems, then red leaf edges, until whole leaves begin to turn.

 "Little Mama" September 22nd  (Hey--gotta call 'em something!)

 October 3rd.

 October 11th.

White ash is quietly going bronze.  This is a fairly unusual color, and handsome rather than gaudy.  Enjoy it while you can: the imminent arrival of the alien invasive Emerald Ash Borer beetle will doom most ashes in the area, even as it has elsewhere in North America.  If you can find a female tree, you might collect a few samaras and plant a tree in your yard; they can be kept alive in spite of borers if treated with the right insecticides.

Samaras (winged seeds) hanging in a female white ash amid a few turning leaves, 
September 25th, October 3rd.

Large and small white ashes, October 10th

One thing that I never cease to marvel at is how parts of a tree will turn quite a long time before other parts.  About this time last year I explained what makes trees turn the colors they do when they do, but this is a different effect.  As animals ourselves, we are most familiar with animal life, in which there is (usually) a brain and (almost always) a nervous system to coordinate changes throughout the whole body.  Plants have neither brain nor nerves.  They also have no circulatory system (heart and blood vessels), though they do have a system of xylem to transport water and minerals from roots to tops, and a parallel system of phloem to transport sugar from leaves toward roots.  (In trees, the xylem is typically in the "sap wood," while the phloem is in a thin layer inside the bark.)  This transport system also serves to move hormones around that work a bit like animal hormones. 

 Local effects of some sort: the entire eastern side of this sugar maple has turned
while the western side is still green.  (October 5th & 10th)

But on the whole, a plant's life is much less centralized and much more "local" than that of animals.  The conditions that trigger leaves to color and then fall act only on those parts of the tree they reach; other parts of the tree must be triggered separately as the conditions vary in time and space.  I remember as a botany student at the University of Rhode Island coming upon a Norway maple tree beside the drive to the Student Union.  A street light was nestled in its branches, and when the rest of the tree was wearing its autumn tint of clear yellow, a globe of leaves around the street light was still green: the night-time glow of the streetlight having prevented the nearer leaves from responding to the longer nights of autumn.  Those leaves remained green as weeks passed and the rest of  the tree became bare, until they finally died shredded to tatters in the winter cold and wind, never really having been "aware" that fall and winter had come.

To put the idea in perspective, imagine standing in very cold water: if you were like a plant, only your feet would feel cold, and only your feet would shiver. 

Such is the diffuse, local life of a tree. 

  I sometimes try to figure out why a certain part of a tree has turned earlier or later than another; it's worth the attempt, I think, though I have never satisfied myself that I knew what subtle gradient of light or temperature from one part of the crown to another had made the difference.  

A few less subtle.

 Poison ivy is worth watching at this time of year--but not too close.  10/10

Virginia Creeper (Parthenocissus quinquefolia) and Flowering Dogwood (Cornus florida) turn partly to attract migrating birds that, here in the city, probably won't come.  9/11, 9/29

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