California Pipevine
By John Hoffman, U. C. Master Gardener
I found my first pipevine growing on my farm, climbing up a tree on the bank of the Napa River. I dug up a section of the vine that had lain on the ground, become covered with leaves and litter, and rooted. I recognized this natural method of propagation as an example of what gardeners call "layering."
I have used this technique many times since planting my little wild pipevine in my garden, to make new plants for friends and for planting at the Martha Walker Native Plant Garden in Napa's Skyline Park. I take a long runner still attached to the parent plant, lay it on the ground, cover a short section with good soil and keep it well watered through the summer. It will root and grow in a few months, and I will have a new plant.
The pipevine flowers are unusual, shaped like a Dutchman's curved pipe. They are green and purple, developing in early spring before the leaves appear. They look like some of the insect-trapping plants of the tropics, but they are not insectivorous.
The pipevine's most delightful trait is its crucial role in the life of the pipevine swallowtail butterfly (Battus philenor). This butterfly has lovely iridescent blue or blue-green wings with seven orange spots on the underside of the hind wing and a wingspan of three to five inches.
The adults feed only on the nectar of a variety of flowers, but the larvae, or caterpillars, feed only on pipevine leaves. The eggs are orange, laid on the underside of the leaves. They hatch to become dark brown caterpillars with four rows of orange spots and numerous soft, horn-like projections. The caterpillars eat a lot of leaves in late spring and early summer, but the subsequent pleasure of having these butterflies decorate my garden is ample payment for the lost leaves.
The pipevine not only has a unique flower but an unusual, six-winged seed capsule. When it matures in late summer, it splits open to reveal a mass of seeds embedded in a soft flesh that the caterpillars relish along with the leaves.
All parts of the pipevine plant, including the seed pods, are toxic to humans. In contrast, caterpillars can ingest the toxins, but then they become unappetizing to birds. Yellow jackets also have no problem cleaning out the pods as soon as they open.
Pipevine plants grow best in semi-shade, in good soil with summer watering. The vines need something to climb on and will send out runners 10 to 20 feet long.
Do not expect the flowers to win any prizes for color, but their shape is interesting and the butterflies they lure provide color to compensate.