Is that thing really a flower?

Wednesday, April 13, 2011

Aristolochia is a genus of vining plants that produce some of the most peculiar flowers imaginable, if it weren’t possible to say that about orchids, too. And like orchids, Aristolochia flowers have male and female parts in the same organ, called a gynostemium (or the column in orchids).

Aristolochia littoralis with one
open flower and buds on right.

There are no petals on an Aristolochia flower, but the whole thing that can resemble a Dutchman’s pipe or a pelican or a number of other odd shapes, is a calyx, or fused sepals. It swells and curves and ends, in Aristolochia littoralis, in a maroon and cream-colored hood. In her book Tropical Flowering Plants, Kirsten Llamas says, “commonly cultivated flowers suggest silk paisley handkerchiefs attached to a drain pipe.”

The vines in good soil (with organic matter added) are growing rapidly now, and a number can be fairly aggressive, but the flowers are so unusual looking that it’s worth the trouble it takes to cut them back in the fall.

Many of the species contain a toxin that is carcinogenic. But, for whatever reason, swallowtail butterflies have selected aristolochias as their host plant. The caterpillars devour the toxin along with the leaves and presumably become bitter tasting to predators.

There are several species in the Garden, including Aristolochia

 A. passiflorifolia, a tiny flower,
in the butterfly garden.

passiflorifolia, which comes from Cuba and the Bahamas and has leaves like passion vines. These flowers are really bizarre with appendages sprouting hair-like whiskers from the end of the calyx.

Flies and insects that are lured into the mysterious opening to the pipe find they cannot climb back out because of backward facing hairs, so they toss and tumble around until they fertilize the flower. The hairs then die and out go the insects.

Look for pipe vines on the vine pergola and the butterfly garden. Follow the swallowtails.