WHY DO MAPLES TURN DIFFERENT COLORS? Posted 12/19/02

•  Rob Johnston, Founder and Chairman of Johnny's Selected Seeds of Albion, ME (Zone 5a) writes in The October Johnny's Selected Seeds Update online newsletter: 

Dear Gardener,

The fall colors in Albion were beautiful and persistent this year. Leaf season began about a week later than usual due, I think (but don't know) to unusually warm September weather in New England. The brilliance finally got underway on Columbus Day weekend, and here it is almost Halloween and we still have a lot of color. Nice. Anybody know why the maples turn different colors -- yellow, orange, or red? Or why the process is timed differently from one tree to another? If you know, drop me a line. 

Our first light frost (31F/-1C) at the Albion farm was October 4. First hard frost (25F/14C) was October 15.

•  I replied to Rob:

Since you mentioned yellow, orange and red, if Sugar Maple (Acer saccharum) and/or Black Maple (A. saccharum ssp. Nigrum) are common wild Maples in your area, the simple answer to coloration, as it is here in our northern Illinois Maple populations, is natural variation within the gene pool. Also, stressed or tapped trees tend to color earlier and more unevenly.

Named varieties of Sugar Maple propagated vegetatively such as the popular Green Mountain, grown under the same conditions, tend to color uniformly and identically. The same is true for Red Maple (A. rubrum) selections such as October Glory and Red Sunset, while our wild populations here are quite variable. Native A. rubrum, as well as the wild forms of the rubrum-saccharinum (Silver) intergrade Acer x. Freemanii (Freeman Maple - which hybridize into multiple generations in our area) are as different as snowflakes.  Anyone who has seen a commercial nursery row (or parkway planting, etc.) of A. x Freemanii Autumn Blaze, Bowhall or Marmo in fall color, however, will immediately notice the uniformity of color (as well as leaf shape, branch structure, head configuration and so on).

The same is true of White Ash (Fraxinus Pennsylvanica) and other colorful native trees with corresponding horticultural selections.

This year in our area, the steady below normal (but not severe) temperatures for three solid weeks (eventually dragged on to three solid months!) have produced a long, drawn-out season of fall color which has held unusually well - we are not normally so lucky!

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