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Outdoors: Aspen trees wear green

This time of year, we often enjoy the Irish street ballad “The Wearing of the Green,” a rollicking tune about the Irish Rebellion of 1798. The song cheerfully proclaims that "they’re hanging men and women for the wearing of the green".

Apparently, it’s historically accurate.

These days, the wearing of the green on St. Patrick’s Day won’t make you invisible to leprechauns, but it probably won’t get you executed either.

For aspen trees, the wearing of the green is a survival strategy.

It’s subtle, but if you look closely at aspen trees, you will notice that the bark, which usually is a dull white, is tinged with green.

This greenish cast, which appears around St. Patrick’s day indicates the presence of chlorophyll in the bark.

So the question is, does photosynthesis occur?

Researchers think so. In fact, a simple demonstration, the iodine test (remember that from middle school?) reveals the presence of starch, which means photosynthesis has taken place.

Of course, photosynthesis — the miracle in which green plants capture the energy of the sun and convert it to food, usually occurs in the leaves.

But in March and April, tree leaves are conspicuously absent.

Scientists speculate that chlorophyll in the bark may give these native trees a jump start on the growing season.

If this is true, it may help explain the success of aspen trees in hostile environments like the Rocky Mountains, the Great Lakes shorelines and even Alaska: all places with short growing seasons.

The aspen trunks will be wearing the green until the leaf out in the forest canopy.

Then, the trunks will become their normal greyish white.

Until then, who knows?

Aspen trunks just might just be invisible Leprechauns.

"Outdoors with Coggin Heeringa" can be heard every Wednesday on Classical IPR.