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Pipevine promotes pollinator health

By FRANCES LAMBERTS

Aristolochia macrophylla was part of the community of the Appalachian mountains’ moist, deciduous forest for at least fifteen million years. This vine in the pipevine family saw ice age glaciations come and go repeatedly yet stayed aboard, helping to build the resilience and great diversity of plant and animal species for which the Blue Ridge region is priced as a botanical “Noah’s Ark” even today.

The Dutchman’s Pipe, its common name due to resemblance of its flowers to Dutch smoking pipes, is also among native, woody plant species vital for pollinator health today.

A 2016 report by Kasten Dumroese and T. Luna, researchers at the U.S. Agriculture Department Rocky Mountain Station, describes “the pollinator crisis in North America.” Habitat loss through development and pesticides are among the well known causes but climate change is emerging as a new, contributing factor.

The planting and promotion of native woody species – trees and shrubs, and vines like Aristolochia or the Trumpet vine – could help quickly, the researchers state, to reverse the serious declines in bees, butterflies, moths and other pollinator insects. If only to protect food production but also to restore other ecological services necessary for health of the environment, they urge, the need to expand native woody plantings in our landscape is “immediate.”

My trellised Dutchman’s Pipe illustrates well the beneficial prospects for pollinator revival which the authors suggest. The vine being the host for one of our beautiful butterflies, the Pipevine Swallowtail, as many as perhaps four dozen caterpillars were born and completed their larval life stage on it this month.

Coming from reddish eggs on stems or the underside of leaves, the emerging caterpillars are tiny, a mere 2 millimeters. As first meal, a caterpillar eats the egg shell for its residual yolk. Feeding voraciously on the vine, it grows to almost 50 mm (about 2 inches) in just two weeks. Then wandering off the vine it spends two days, as observed by Don Holt of the Mountain Empire Butterfly Club, seeking some structure and spinning a silk web and girdle to anchor itself, as pupa, to it. The adult swallowtail butterfly emerges two weeks later.

For protection, the newly hatched caterpillars stay and feed together. But imparting a poisonous acid, the vine makes their tissue distasteful and toxic to predators. As they grow and develop the visual cues – bright red spikes on a velvety, maroon-colored body – the caterpillars become solitary. The toxin so effectively protects the Pipevine Swallowtail throughout its (egg to adult) life stages that several other butterflies mimic its appearance, also to gain predator protection.

Aristolochia’s flowers are pollinated by flies but the butterfly it nurtures, in its nectar-seeking visits helps pollinate bee balm, lupines, phlox, verbenas and quite a range of other flowers.

The vine also has ornamental uses, quickly providing “dense cover for sun porches, verandas, pillars, posts, arbors, fences or walls,” as the Missouri Botanical Garden notes. Having lived in the moist Appalachian forest for these millions of years it, too, is sensitive to drought, however, under ongoing, man-made climate change.