Springing Out

The vibrant green of the vernal season – including new sassafras leaves and unfurling fiddlehead ferns – is a welcome sign of renewed activity in the natural world.

Spring on Martha’s Vineyard: Late March talks a good game, and April and May, throttled by the ocean’s lingering chill, don’t deliver. Not until June is the Island truly safe from seasonal relapse.

But those of us with a close eye on nature see and hear a seasonal process that is, if possible, even more protracted and complex. As early as mid-January, lengthening days prod chickadees, cardinals, and house finches back into musical mode. Progress from there is slow, erratic, but almost always perceptible. A surprising diversity of plants and animals have begun, or even completed, key pieces of their life cycle before the typical Vineyard human dares to think of spring.

Tying stages of your life to a fickle season is risky. Plants and animals active in early spring can face lethal consequences from arctic cold or a massive snowfall, and even in a routine season, they must contend with short days and sub-freezing temperatures. But there are advantages for the early riser. Adversity in nature equals opportunity for any species that can evolve a way to overcome it.

On the plus side, predators and competitors are few in early spring. Ground-hugging plants grow unshaded by their taller, but still leafless, rivals. Early-season insects, relatively safe from assault, bask in sunlight with impunity to keep their bodies at operating temperature. Many of these species are colored black or brown, unobtrusive amid last year’s dead leaves while also absorbing as much of the sun’s heat as possible. If you’re a flower requiring pollination by insects, the few that are active will reliably sniff out whatever blooms you have to offer. And while drought can easily interrupt plant growth during a Vineyard summer, water is generally plentiful in early spring.

This spring vanguard is an elusive crew, specialized in their behavior, physiology, and interactions with other species, and often associated with very specific niches or microclimates. To me, these quirks and talents are fascinating in and of themselves, examples of the endless creativity of nature. But don’t mistake these early-season plants or animals as mere oddities: What happens in spring affects the Island through the rest of the growing season, and even into years to come.

Skunk cabbage

Central heating and an alluring aroma.

For a sterling example of a plant adapted to early spring, head to the nearest swamp. Aptly named, skunk cabbage will be flowering there as early as late February in a mild year. A purplish, hooded structure – about six inches tall when fully grown – passes for a flower on this plant. Within the hood is a dull yellow, club-shaped object, tufted with bristles that can both produce and receive pollen.

The whole assembly possesses a talent rare in the plant world. Skunk cabbage ramps up its metabolism to produce heat through a sort of chemical shivering, known as thermogenesis. It allows the skunk cabbage flower to grow in the cold, even melting its way up through residual snow. But it also makes the interior of the flower a toasty refuge for any insects active then. Some of these may transfer pollen from one flower to another, enriching the genetic health of the skunk cabbage population.

The fetid smell of the flower holds special appeal for a group of insects optimized for early spring activity: the so-called flesh flies, for whom the carcasses of animals that died over the winter represent a gradually thawing food source for developing larvae. Lingering inside the flower because of the warmth, flesh flies are custom-designed pollinators for this bizarre plant.

The lush green leaves of a skunk cabbage appear shortly after the remarkable flowers, and to look at them, you’d think these leaves, uncannily similar to hosta in a summer garden, would be devoured by deer and other herbivores. But no.

In addition to its unpleasant odor, skunk cabbage packs a physical wallop. Sharp, microscopic crystals of the chemical compound calcium oxalate form in the tissues of the plant, and thus anything that tries to eat the leaves will have these irritating particles wedged in its mouth, imparting a furious burning sensation that lasts for hours (yes, as a curious ten-year-old I once tried eating skunk cabbage).

Invasive species

Getting a head start on some natives.

In addition to native plants adapted to grow in early spring, the Vineyard hosts many exotic species that break dormancy before the baseball season is in full swing. Many of these – snowdrops and crocuses, for instance – naturalize inoffensively in lawn or garden, encouraging us with hints of cheer as winter begins to fade.

But some other exotics – autumn olive (right) may be the best example – leaf out early to much less benign effect. Such invasive plants, freed of the insects or competitors that hold them in check in their native ranges, can choke out the native vegetation of their adopted home, reducing diversity and displacing resources for native wildlife.

Getting a head start on the season can allow exotic plants to shade out native competitors. And an early start also guarantees them a long growing season, affording maximum time for growth, root extension, and seed production. Botanists evaluating the invasive potential of newly introduced plants include early leaf-out among their warning flags.

Early green

Color and chemistry in young leaves.

For the human observer, much of the sensory appeal of spring comes from the season’s unique palette of colors. While leafing out, the oaks that dominate our woodlands (left) show an ethereal green, immature leaves, and catkins of flowers producing a hue dramatically different from the hard green of summer. But for many of our plants, the start of the growing season represents a pivotal moment of vulnerability in an ongoing chemical war against insects.

A surprising number of plants produce chemicals aimed at discouraging leaf-eating insects. In the case of oaks, for example, a group of bitter chemicals called tannins makes mature leaves unpalatable, or downright inedible, for insects that haven’t evolved a particular knack for processing these compounds. But in general, the levels of these defensive chemicals start low at leaf-out, climbing steadily as the foliage matures.

Certain insects, like the fall cankerworm (left, which is native) and the winter moth (right, which isn’t), exploit this pattern, hatching early in the season so their caterpillars can feed on the youngest leaves, while tannin levels are low. But the strategy involves a gamble on the part of the moths. Hatch too late, and you miss the most edible leaves; hatch too early, and cold weather will inhibit your ability to feed (or simply kill you). But hit the sweet spot, and an unlimited supply of food translates into a huge flight of fertile adults.

Consequently, the abundance of these caterpillars can vary widely from year to year, while the damage they do to trees ranges from negligible to catastrophic. Young foliage, then, is at the center of a complex dynamic with profound effects on the health of our woodlands.

First flowers

Repercussions well beyond springtime.

In April sometime, a run of true spring weather coaxes out the frail, white blossoms of shadbush or serviceberry (above) – a spindly, black-barked tree found mainly in up-Island woodlands (it’s called wild pear by some old-time Vineyarders). Soon to follow are the flowers of beach plums, cherries, and apples. Whether native or cultivated, these plants are all closely related, sharing a five-petal flower structure and at least some measure of reliance on pollination by insects, especially bees. In a different plant family are our half-dozen or so blueberry species, producing clouds of bell-shaped flowers (right) that are a favorite resource for bumblebees and many of our earliest butterfly species.

Supporting insect pollinators is an important ecological function of these plants. Flies, wasps, ants, moths, and beetles, in addition to bees, may visit fruit flowers. They function in turn as predators, prey, or parasites, supporting or helping control populations of other insects. I’ve even noticed that orioles, those quintessential, fiery-feathered birds of summer, often visit apple blossoms for nectar and perhaps an insect snack in the days following their return to the Island. But the fruits of these trees and shrubs, which vary in abundance according to the success of pollination, play still more obvious roles later in the season. Some, of course, such as apples and beach plums, will furnish foods or income for human Islanders. Smaller fruits, like the tiny berries of the shadbush, will help sustain a host of songbirds – a resource that is especially critical during the energy-demanding period of fall migration.

What happens in spring echoes throughout the rest of the year, and even beyond. From the first hints of lengthening days, plants and animals respond, their instincts and adaptations engaging in a complex dance with sun and storm, and with a web of other species. Each spring season, with its unique conditions, exerts pressure on wildlife, favoring some populations, depressing others. And in the seasons that follow, the outcome of this grand, complex struggle shapes the landscape in ways that matter profoundly, even as they defy our full understanding.