Evolutionary Allies: Native Wildflowers and Insects

You can enliven the landscape and help cultivate the Island’s rich ecological diversity by planting wildflowers.

To start with an obvious point, plants can’t see. So what’s with all the flowers? The answer, of course, is that flowers are aimed not at the plants themselves, but at animals, mainly insects, bound to plants in a mutually beneficial partnership.

Drawn to eat pollen or drink nectar (energy-rich liquid produced by flowers precisely to reward visiting insects), an insect brushes the male organs, or stamens, of flowers, picking up pollen grains on its body. Upon visiting another flower of the same species, the insect may leave some of the pollen it carries on the female organs, or pistils, fertilizing the flower and making seed production possible. This exchange, food for fertilization, ranks among the most crucial of all biological processes. In evolutionary terms, it drives ecosystems and it shapes the life histories of untold thousands of species.

As gardeners, we typically judge a flower by its appeal to humans. But a garden or a landscape looks quite different if we view it with the biological purpose of flowers in mind. In particular, this perspective puts a spotlight on our native wildflowers – a foundation of the Vineyard’s ecosystem.

The importance of pollination by insects can be judged by the investment that plants make in producing flowers. To be sure, some plants – pines, oaks, and grasses, for example – simply dump their pollen into the breeze, hoping luck will bring a few pollen grains to receptive organs. The flowers on such plants typically lack the scent, structure, or color that would attract insects, but the amount of pollen they produce is necessarily huge (most of it ending up, it seems, on car hoods and patio furniture). Some other plants can fertilize themselves, either routinely or in the absence of cross-fertilization. But this approach, while self-sufficient, surrenders the genetic advantages of interbreeding.

Insect-pollinated plants, in contrast, hire a delivery service: Their investment goes not into pollen production but rather into producing attractive flowers, typically plentiful, sometimes large, and usually colorful. The process of evolution – favoring what succeeds – has refined the appearance, structure, and arrangement of flowers in a multitude of insect-pleasing ways. One pleasure of studying our native flowers is seeing how adept they are at serving insects. For example, a butterfly weed’s bright orange panicle held aloft over the plant itself makes a target that can’t be missed. Once a wasp settles onto this garish landing pad, it methodically explores the scores of individual flowers, guaranteeing it will depart well-fed and bearing a healthy dose of the plant’s genome.

Since a long bloom period ups the odds that pollinators will discover a flowering plant, many of our native plants keep blooming over an extended period. Mountain-mints, for example, produce multiple flower heads over a period of weeks; on each head, an individual flower or two opens each day, and the blooming period for the plant may approach two months. On the candelabra-like flower heads of vervain (also called verbena), individual blooms open in sequence from bottom to top on a handful of spikes, prolonging the bloom period while creating an attractive density of flowers.

Butterflies may be the best-known pollinators, popular and sometimes conspicuous insects (though a surprising number of the eighty or so butterfly species that have been found on the Vineyard are small, drab, or both). But hundreds of different bees, wasps, flies, beetles, and moths, native and exotic alike, also pollinate the Island’s native flowers. Many, closely observed, rival flowers in beauty, and all are worth learning about.

Some pollinators show a special fondness for particular plants: Crossline skipper butterflies, for example, simply adore a good thistle blossom. Likewise, pollinators vary at how effectively they transmit the pollen of a particular flower. For these reasons, one wants a high diversity of both native flowers and pollinators, to make sure that each species finds its match.

The honeybee, a non-native insect valued for agricultural pollination as well as honey production, is generally not a very effective pollinator for our native wildflowers, studies have shown. A foreign import, it competes aggressively with native insects for pollen and nectar – both finite resources. The bee is a fascinating creature, but its contribution to food production may say less about honeybees than it does about how modern agricultural methods have damaged native pollinator populations.

Not only providing sexual surrogacy for plants, insect pollinators play other ecological roles as well. They are prey for birds, larger insects, and smaller parasites; spiders, sometimes colored for camouflage on particular species, lurk on flower heads to snag visiting pollinators. As parasites or predators themselves, pollinators effectively regulate populations of other insects, preventing or curtailing outbreaks of excessive abundance. The foliage of wildflowers feeds still other insects, the larvae (for example, butterfly caterpillars), or the pollinators themselves. Native wildflowers, plus the insects they interact with, foster natural abundance of all kinds and contribute to a healthy, resilient ecosystem.

Gardening with wildflowers, though, demands aesthetic recalibration. Evolved for a partnership with insects, few of our native flowers approach the flashiness of exotic ornamentals, or even of horticultural varieties of native species. (Commercial horticultural shenanigans, such as the “doubled” coneflower varieties featured in some popular mail-order catalogues, ruin perfectly good nectar plants by warping effective flowers into something insects can’t figure out how to tackle.) The beauty of wildflowers is often most apparent up close. Above all, native-plant gardening is for those who value nature over artifice and find aesthetic value in diverse and vibrant wildlife.

Many of our native wildflowers do well in cultivation, living or re-seeding indefinitely in border, bed, or meadow. But others can be surprisingly fickle, adapted to flourish only with a certain soil type or moisture regime, sometimes requiring prolonged cold periods or scarification of the seed coat to germinate. Some natives begin life as so-called “hemiparasites,” their tiny seedlings tapping into the root system of a specific host species to get a head start. Still other natives spend their first few years developing their root systems rather than their top growth. So serious native-plant gardening is an activity for the patient gardener who likes to experiment.

But there are plenty of native nectar plants that anyone can grow – a Vineyard gardener can’t go wrong with butterfly weed, sickle-leaved golden aster, seaside goldenrod, or stiff aster, all widely adapted to the Vineyard and readily grown from seed. Common milkweed, blossoming in early summer, grows almost too readily, and its flowers attract nearly everything. Swiping whole wild plants without permission is definitely wrong, and even the seeds of rare species should be left in the wild. But the discreet removal of a few seeds of common wildflowers? I know I’d never object. So one way to plunge into native-plant gardening is simply to work some seeds from wildflowers you like into lightly cultivated soil in a bed or border. Let them overwinter and see what comes up.

The phrase “native wildflower” is a slippery one. In its strictest sense on the Vineyard, it means Island-origin stock of a species that occurs here naturally. (Such plants are hard to come by commercially; some are sold by Polly Hill Arboretum in West Tisbury and some occasionally by for-profit nurseries.) True Vineyard natives are surely best for our native pollinators, but off-Island stock of Vineyard native species is much easier to obtain and probably works just fine for pollinators. At the other end of the spectrum, in the plant industry, “native” often means “from somewhere in North America,” and such plants may or may not work well on the Vineyard.

Many more “near-natives” – well-behaved plants that originate on Vineyard-like soils elsewhere in eastern North America or even beyond – are readily available, grow well here, and serve our native pollinators as well. Coreopsis, coneflower, blanket-flower, and black-eyed Susan are examples. And many plants from farther afield are popular with our native insects and don’t appear to show invasive tendencies: The flowers of most culinary herbs (thyme, marjoram, oregano, and so forth) attract swarms of small insects, while butterfly bush, a shrub of Asian origin, is simply a miraculous magnet for pollinators. From an ecological perspective, true Island natives can’t be surpassed. But for reasons of practicality or preference, flexibility in plant choice may be necessary on the Vineyard. The point is to garden with an eye toward insect life as well as flowers, and to think of one’s garden not as an isolated space but rather as a specialized component in a larger ecosystem.

Native-plant gardening creates new plant populations and new opportunities for pollinators. But it’s only one way to study and promote these important flowers. You can appreciate them in the wild; Newcomb’s Wildflower Guide (Little, Brown and Company, 1989) and a pocket magnifying glass will get you started. And you can do wildflowers and the whole Island a favor by supporting the Vineyard’s nonprofit land conservation efforts. But however you approach these important plants, keep in mind that their beauty is only half the story – they’re vital links in a biological web that sustains us all.