Something Wild: N.H.'s other foliage season

"Something Wild" is joint production of NH Audubon, The Society for the Protection of New Hampshire Forests & NHPR. We recommend listening to it in its original format on NHPR but a transcript of the show is also below.

You can hear Something Wild on-air at NHPR every other Friday at 6:45 a.m. and 8:45 a.m., or subscribe to the Apple podcast here.

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If you’re a new transplant to New Hampshire, you might not have noticed our “other foliage season.” Each spring, tiny tree flowers and swelling buds, ready to burst, paint a subtle wash of early pastel color across our hillsides and wetlands.

Colorful twigs are not as exuberant as flower blossoms. We don't get bright March cherry blossoms like D.C. Maybe we try to compare our northern surroundings to warmer climes too soon and feel inadequate. But we are New Hampshire yankees; suffering is the wellspring of our stoic character.

Even if you’re a long-time Granite Stater, and have learned to appreciate this so-called “micro-season,” you might not know what’s really taking place during early bud-burst.

The colors spread from the coastal plain where spring arrives earliest to the ridges of the Monadnock Region, and eventually to the White Mountains. The trees and shrubs that color the landscape as winter fades include the unmistakable stems of red-osier dogwood growing in wetlands. Bright red buds swell on red maple twigs, and the bark and bud scales of the youngest twigs on apple trees appear rosy on warm sunny days.

Yellow canes of weeping willows brighten the early spring landscape, and the smooth gray bark of twigs of young poplars, including trembling aspen and cottonwood, all develop a greenish tint well before their leaves appear. Our state tree, the paper birch, has a dark maroon tinge on its young twigs. And so does pin cherry, another thin-barked species.

These trees are all fast-growing, sun-loving “pioneer species” which make up New Hampshire’s young deciduous forests. They grow fast in full sunlight and compete well in the botanical relay race called “succession.” These trees are vying for prominence and fighting for their share of the wealth, which in this case are resources like light and nutrients.

There is a strategy behind twig and bud scales sporting bright colors. Those pigments allow them to get a head-start on photosynthesis, converting sunlight into sugars, to produce new growth even before leaves emerge.

The vernal window of springtime photosynthesis opens early with stronger sunlight and warming temperatures. Thin bark on these fast-growing species, sometimes called photosynthetic bark, allows sunlight to more easily penetrate. Many use a pigment called anthocyanin to capture and convert light at the red end of the spectrum.

Even low-growing alpine plants, buried under snowpack until late May, can produce sugars well before the snow is gone by using this same pigment. Longer wavelengths of light in the red spectrum penetrate deeper in the snowpack allowing plants to start producing sugars even before snowmelt.

Above the snowpack, look at twigs in early spring; many are green just beneath the bark. This ability to photosynthesize before temperatures are warm enough for leaves to safely emerge is an adaptation for cold climates. Tender leaf tissue can easily be damaged by freeze and frost.

Contrast this to trees without photosynthetic bark - sugar maples, for example. They rely on converting starch that is stored in roots, but was produced in leaves the previous summer. It has to be re-converted back into sugar and sent all the way back up the stem to fuel developing leaves.

It is all about sunlight. As you see the sticks and twigs of the “other foliage season” develop color with the arrival of more sunny late-winter days, it’s a proxy for when sap is flowing. Yellow weeping willow stems tell sugarmakers that maple sap is coursing in the taplines of the sugarbush.

Something Wild is a joint production of New Hampshire Audubon, the Forest Society, and NHPR and is produced by the Team at Outside/In.