The science behind colorful fall foliage and an interactive map of where you can find it

Colorful fall foliage in Fort Kent. (BDN file photo by Julia Bayly)

Colorful fall foliage in Fort Kent. (BDN file photo by Julia Bayly)

Living in Maine, it’s easy to take foliage season for granted. The once green trees all around you start to turn varying shades of warm colors, like yellow, orange and red, and eventually fall off, leaving the bare limbs we’re accustomed to throughout the winter.

Those weeks of bright colors are great, though. People come from miles around to find the best spots to see the blazes of orange and red reaching across the horizon — it’s a once-a-year tourist attraction Mother Nature begrudgingly offers us before shoveling, er, skiing season.

So the fall foliage season is great. Now raise your hand if you know why it happens.

According to vacation lodging service, as well as grade school science teachers everywhere, leaves get their green color from Chlorophyll cells, which convert sunlight into the glucose that energizes plants.

But as the days shorten and sun lowers on the horizon, Chlorophyll has less light to use and the trees’ production of those cells slows to a stop. In some cases, the disappearance of Chlorophyll allows us to see the colors generated by other underlying compounds that are always present, but only visible for a handful of weeks in the fall.

Those compounds include beta-Carotene — which absorbs blue and green light, and reflects red and yellow light to shine as orange to our eyes — and certain flavonols, which are proteins that help give leaves and egg yolks alike their yellow colors.

Some trees in the fall ramp up production of anthocyanins at the same time they’re cutting down the production of Chlorophyll cells. Anthocyanins produce a red hue and help fortify the leaves against the coming cold season, so they can hang on as long as possible.

Eventually, however, the trees’ self preservation processes kick in and the leaves fall for the winter.

Here’s how explains:

“If trees did not shed their leaves, their soft vegetation would certainly freeze during winter time, damaging and no doubt killing the tree. In order to cope with the gruling winter temperatures, trees slowly close off the veins that carry water and nutrients to and from the leaves with a layer of new cells that form at the base of the leaf stem, protecting the limbs and body of the tree. Once the process of new cell creation is complete, water and nutrients no longer flow to and fro from the leaf — this enable the leaf to die and weaken at the stem, eventually falling gracefully to the ground.”

Why all this from Well, because they have one of those interactive maps we like so much.

Theirs allows users to scroll week-by-week through the fall season to see when the foliage is expected to change across the country.

Peak season for most of Maine, the map shows, will be around Oct. 10 of this year, with the southern corner and some coastal spots hanging on until the following week.

Wes Melton, an engineer who worked on the map, told his team used “an algorithm to predict when leaves will peak in each area of the country.”

“While — scientifically — the concept of leaves changing colors is fairly simple, the ability to accurately predict when they will peak is very difficult due to the number of factors,Melton told the website.

The SmokyMountains folks think they have it all figured out, crunched the data and produced the predictive map found here. See what you think and plan your vacation accordingly.