Natives and Transplants

In nature, not all flowers are created equal.

blue flag irises

Known as blue flag, Harlequin blue flag, or simply blue iris, the native Iris versicolor flowers in the early summer. Peter Ralston shot this stand on a small, private island in Penobscot Bay, “one of those secret island treasures . . . that I have sworn to my friends I will never identify in print.”

By Phillip Conkling
Photo by Peter Ralston
From our May 2023 issue

We say that April showers bring May flowers, but there is also a coda: in nature, not all flowers are created equal. Such has been the mantra of Doug Tallamy, an author and professor of ecology at the University of Delaware. I saw Tallamy speak three years ago, at the Martinsville Grange, in St. George. He grew up loving both flowers and the insect life around him, and as a professional ecologist, he understands better than most that you cannot have one without the other: flowers depend on insects for things like pollination, while insects depend on flowers for food.

As a young scientist, Tallamy loved to plant gaudy, colorful gardens, until he began to realize that those showy nonnative plants didn’t support the showy butterflies he also loved seeing. Nor did he see as many moths — or even crawly caterpillars. He made the connection between native plants and insect abundance and diversity. And he writes today that a land without insects is a land without most forms of higher life.

So beginning in his own backyard, Tallamy eliminated alien species in favor of native ones and noticed slow but steady increases in the bees and butterflies that depend on them. With careful tending of his native trees, shrubs, and garden plantings, he saw an increase in the number of birds that depend on the proliferation of juicy moth and butterfly caterpillars. From Tallamy’s startling recognition came an even more radical idea, that the only viable strategy to increase biodiversity across large swaths of America is to restore native plants everywhere, one backyard at a time. 

My wife is a talented gardener, and I am a forester. We have been working, with mixed results, to implement Tallamy’s insights on a parcel on the mainland and another on an island. We have always been ruthless in eliminating introduced bittersweet and the tenacious introduced barberry bushes that love old fields. Surrounding one granite outcrop, we have replaced a ring of nonnative daylilies, originally planted by a beloved ancestor, with a border of stunning blue-flag irises. In our mainland flower garden, my wife — a native, unlike me — has always planted native flowers, including hydrangeas, asters, delphiniums, Solomon’s seal, and cosmos. Last summer, we were stunned to watch a great hummingbird hawk-moth use its long, straw-like feeding tube to suck nectar out of white phlox in the garden. But we also love our nonnative globe thistles and English lavender. They may be introduced from Europe, my wife points out, but they are also beloved by our native bumblebees and honeybees. 

Tallamy is also a great lover of oaks, and here we encounter another dilemma. He describes the spectacular abundance of caterpillars that oaks support, pointing out that birds also love oaks, for providing them with handy packets of protein- and fat-rich caterpillars, especially when voracious nestlings need to be fed. However, our oaks are the favored overwintering site for the pestiferous nests of brown-tail moths. When those caterpillars hatch, their nasty spiky hairs cause serious skin rashes on my favorite gardener. So we have been forced to turn a dozen of our oaks into winter firewood. We have, however, kept one old, hollow giant, which provides roosting spots for the owls we occasionally hear. 

In our garden and woods, not all natives are equally beloved, and not all nonnatives are unwelcome aliens. Among Maine trees and garden plants, as among its two-legged mammals, we can only hope to strike a careful balance.