Fall Leaf Se­crets Re­vealed

Find out why leaves change color and where to catch the show.

Birds & Blooms - - Contents -

KATHY MATHEWS LOVES TO WATCH THE SU­GAR MAPLES turn yel­low, or­ange and red at Great Smoky Moun­tains Na­tional Park near her home. “Some­times you’ll see all three col­ors on the same leaf,” she says. An as­so­ciate pro­fes­sor of bi­ol­ogy at Western Carolina Univer­sity, Kathy has spent 10 years study­ing and pre­dict­ing peak view­ing time for fall col­ors. She still mar­vels at the magic of fall, when green leaves trans­form into bril­liant eye-catch­ing cop­per shades. This phe­nom­e­non oc­curs when trees stop pro­duc­ing chloro­phyll, a green sub­stance in leaves that in­ter­acts with sun­light through­out spring and sum­mer to make food for trees to grow. Chang­ing weather con­di­tions in fall tell the trees it’s time to store sug­ars in the roots for next year’s growth. As the cool tem­per­a­tures ap­proach, day­light hours shorten and the chloro­phyll breaks down, re­veal­ing the bright hid­den hues.

“It is more ef­fi­cient for the tree to do this than to main­tain its leaves year-round,” Kathy says. Some trees, in­clud­ing maples, even cre­ate a new pig­ment—a deep rich red.

Weather con­di­tions in the spring, sum­mer and fall af­fect the tim­ing and the bright­ness of au­tumn leaves. A dry sum­mer may mean more vi­brant col­ors, Kathy says, “although that’s not good for the over­all health of the tree.” On the other hand, a rainy sum­mer re­sults in duller hues. And a sunny, dry fall pro­duces more of the deep red pig­ments.

“For the best fall color, you want a grad­ual but steady tem­per­a­ture change,” Kathy says. “You want the night­time tem­per­a­ture to con­tinue to dip to freez­ing to make all of the trees come into full color at once.”

And that’s when the magic hap­pens. This an­nual spec­ta­cle oc­curs all over the coun­try, so you can en­joy it in your town or even your own back­yard. Many folks, how­ever, pre­fer to catch the show on the road. When plan­ning an au­tumn color view­ing va­ca­tion, it’s best to set aside sev­eral days to a week.

Kathy rec­om­mends check­ing the time of the av­er­age an­nual first frost at your des­ti­na­tion. “Plan your va­ca­tion for a cou­ple of weeks after the first frost, to hit color at its peak,” she says. “A freez­ing tem­per­a­ture is what starts the break­down of chloro­phyll. You can pre­dict leaves will start chang­ing about three or four days after the first frost.” She also sug­gests vis­it­ing web­sites for the places you want to go to learn more about typ­i­cal fall color pat­terns.

Be­cause of the un­pre­dictabil­ity, visit an area with var­i­ous el­e­va­tions for the best chance of view­ing many col­ors across the land­scape in one day, says Paul Su­per, science co­or­di­na­tor at the Great Smoky Moun­tains Na­tional Park.

“In the Smok­ies and in other moun­tain­ous ar­eas, the peak time for color changes with el­e­va­tion,” he says. “You can come over a wide range of days, and the fall col­ors pass peak at high el­e­va­tions ear­lier than the low el­e­va­tions.” High spots in the Smok­ies, with a cli­mate sim­i­lar to New Eng­land, see yel­low birch turn bright yel­low amid the reds of mountain ashes, some­times as early as mid-septem­ber.

At lower el­e­va­tions, you can ob­serve peak col­ors of su­gar maples, hick­o­ries, sweet­gums and other trees from early to

mid-oc­to­ber through early Novem­ber. Paul sug­gests not over­look­ing oak trees, which are among the last to change col­ors. They pro­duce rus­set, red and yel­low-brown leaves, de­pend­ing on weather con­di­tions.

No mat­ter where you are in fall, re­mem­ber that the nat­u­ral world is con­stantly chang­ing. “You have to take your chances on when the best col­ors will ar­rive,” Paul says. “But you’ll al­ways find some­thing beau­ti­ful.”

Sheryl Devore lives in north­ern Illi­nois where lo­cal for­est pre­serves abound with or­anges, reds, yel­lows and other hues in mid-oc­to­ber. She’s also trav­eled to the Great Smoky Mountain Na­tional Park to ex­pe­ri­ence fall col­ors at var­i­ous el­e­va­tions.

A cute tufted tit­mouse amid a sweet­gum tree's bright fall leaves.

A dap­pled sas­safras leaf rests on the dark ground.

Cruise 70-mile Mil­lion Dol­lar High­way through Colorado to see epic fall color.

Fran­co­nia Notch State Park in New Hamp­shire comes alive with cop­pery hues.

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