by Patrick McMillan
The past couple of weeks the small, freakish flowers of one of the strangest of plants have begun to open in our gardens – pipevines. It’s difficult to believe that nature could summon up anything as strange as the flowers of pipevines. If you remember the “regular” aka actinomorphic and the “irregular” zygomorphic flowers from high school biology then you would have to consider the strange, inflated flowers of pipevines highly irregular.
These plants are related to wild gingers/heartleafs (Asarum) and are members of the basal angiosperms, which are plants with lineages that predate monocots and true dicots. Many of the early angiosperms have flowers that are pollinated by flies or beetles that they lure to the flowers with the pleasant smell of rotting meat or dung. Pipevine is no exception. They trick flies into entering the strangely shaped flowers which often have a funnel-like flare with a narrow opening and trap the fly in a chamber with the pollen and nectar to accomplish pollination.
The general shape of the pipevine flower also approximates the anatomy of a uterus and birth canal. As was all the craze in the early years of medicine, the resemblance to the uterus must mean it is good for treating issues with difficult pregnancies and childbirth. This archaic mode of determining herbal remedies is referred to as the doctrine of signatures – basically if a plant part looked like a part of the human anatomy it would be used to treat ailments associated with that organ. This avenue of medical care led us to the highly unsuccessful use of liverleaf (Hepatica) to treat ailments thought to be caused by the liver, like cowardice and freckles. Medical science has since progressed, maybe?
The pipevines include herbaceous upright perennials, short rambling vines, and enormous lianas (woody vines). The toxic chemical aristolochic acid is contained in all parts of the plant and though it is known to cause kidney failure (which probably didn’t decrease the problems with difficult childbirth) this chemical has also been shown to have antitumor properties. Don’t go munching on the leaves! Pipevine Swallowtails depend exclusively on pipevines for their larval food source and all the species we grow are host to large numbers of caterpillars in the summer.
The Pipevine Swallowtail accumulates aristolochic acid which deters predators like birds from wanting to consume them (they don’t want kidney failure either). This may explain why Spicebush Swallowtails and Red-spotted Purples look so similar to the Pipevine Swallowtail, they’re taking advantage of blending into the poisonous crowd.
These beautiful butterflies always seem to find your pipevines, no matter how secluded you think they are. Don’t worry, we can’t have enough swallowtails and the vines regrow without issue. These are great plants to include in your garden to support our butterflies. The caterpillars have another interesting behavior, when disturbed they have bright orange “horns” that are technically referred to as osmeteria that it pushes out of the front of its body and emit a very foul odor!
Three native pipevines are found in the Carolinas. Common Pipevine (Isotrema macrophyllum) can become a huge liana, reaching the canopies of old-growth trees and spreads through runners and can be difficult to keep contained. It grows best in cool climates and tends to suffer or not grow in warmer parts of the Southeastern US.
Woolly Pipevine (Isotrema tomentosa) grows very well in hot, humid climates and is known from only a few native populations in the Carolina coastal plain. Like its mountain cousin it is very difficult to restrain and may quickly outgrow the space you envision for it.
The only other pipevine is very dissimilar to the others, Virginia Snakeroot (Endodeca serpentaria), which is an upright herbaceous perennial that rarely gets a foot tall. If you’re wondering why these former Aristolochia are now in the genera of Isotrema and Endodeca, well, it appears to all be about genetics. They are closely related but currently in different genera.
One of the easiest to grow and showiest, best-behaved species in our garden hails from Brazil, Argentina and Bolivia, Fringed Pipevine or Fringed Dutchman’s-pipe (Aristolochia fimbriata). The plants form scrambling vines that act more like a groundcover than a vine and have beautifully silver-veined small leaves. The flowers are intricately patterned with lines and fringed with long “tentacles” to create one of the most bizarre flowers you’ll ever include in the landscape. Though you wouldn’t pick a plant from Brazil to be rock-hardy here in Raleigh, this one has been fully hardy (zones 7a-9a). For those of you looking to add some swallowtails but unwilling to devote the space to a monstrous mass of vines this one is for you. Fringed Pipevine is also incredibly drought-tolerant and perfect for part-sun to dappled dry shade.