I remember exactly where I was the first time I saw a pipevine swallowtail. My husband and I were hiking on East Ridge Trail in Redwood Regional Park when a spectacular blue butterfly fluttered by. It was big—about five inches across—and I had never seen a butterfly that color, an iridescent blue. It looked exotic, almost tropical. “What was that?” we wondered aloud as we followed it until it disappeared into the trees.
I learned it was a butterfly with a single host plant genus for which it is named: the pipevine, Aristolochia. In California there’s just one native species of Aristolochia, California pipevine (Aristolochia californica), a highly toxic plant that nevertheless provides the only food for pipevine swallowtail caterpillars. It grows wild in riparian and forest habitats in Contra Costa and parts of Alameda County. Outside of Northern California, pipevine swallowtails are found in much of the southern U.S., where their larvae feed on different Aristolochia species.
I was certainly not the first to be bewitched by this butterfly. A CBS news story on a biologist named Tim Wong set off a flurry of interest. He raised pipevine swallowtails in a protective greenhouse in his backyard, where he grew Aristolochia. Later, he released the butterflies at the San Francisco Botanical Garden, where he first got the clippings of the vine.
One of the people who saw that news story was Jim Spinello, in Alamo. A veteran at raising butterflies, he’d seen the swallowtail flutter through his yard, so he set out to grow Aristolochia. A year after he planted it, he found eggs on the vine.
Don’t get your hopes up. This is not the typical experience: most people don’t see the butterflies for a few years after they plant Aristolochia, if ever. Spinello just happens to live in a corridor or flyway with an established population.
As for its host, Aristolochia usually takes several years to get established, and longer still to become large enough to host the butterfly colony. It also becomes huge, with vines up to 20 feet long, sprawling out or climbing into trees. This makes it impractical for many Bay Area yards.
Although it’s known as a riparian plant, it thrives in many gardens with no creek on site, as long as it gets water until it’s established. Experts say the basic rule is plant its roots in the shade in a spot where it’ll be able to grow into sunlight.
In that first year, Jim Spinello’s young vine was not big enough to sustain his hungry caterpillars. He had to search for more Aristolochia to feed them, and in the process he began making connections with others who grew the vine.
The following year, he had so many larvae, he had to farm them out to foster parents, or as he calls them, caterpillar-sitters.
This year, he farmed out 300 larvae and currently has 200 in chrysalis, where they will stay until they emerge next year. This “overwintering” always comes as a shock for caterpillar-sitters, who inevitably ask, “Did you say NEXT YEAR?”
That was not a deterrent for Terry Smith, a retired science teacher who was one of the co-founders of the “Pollinator Posse,” a non-profit that encourages gardeners to plant eco-friendly landscapes with pollinators in mind.
Terry Smith planted her vines in Piedmont eight years ago and was one of those caterpillar-sitters who found larvae through like-minded folks in the Pollinator Posse. Even then, it took two years before she was successful, finding 200-300 eggs on her plants. She, like Spinello, had to find caterpillar-sitters to feed all her hungry offspring.
At East Bay Wilds Native Plant Nursery in Oakland, owner Pete Veilleux says the demand for Aristolochia has been growing so much that it’s been hard to keep it in stock. This last year, he estimates he sold about 2,000 plants! Most of those customers said they were trying to attract the butterfly.
Out in the wild, according to Veilleux, Aristolochia californica does best on moist slopes facing north or east, on the edge of wooded areas—for example, where there is a road cut so the vines can get sun either in the morning or afternoon. Veilleux grows his plants from cuttings. He agrees they can take a long time to grow but says you can speed that up by watering them well and adds, “It can be trained on a fence, particularly a chain-link fence, making it better for use in yards.”
Before you get all excited, some honest full disclosure here. My own experience with Aristolochia californica has been mixed.
Through the Pollinator Posse, Terry Smith, entomologist Eddie Dunbar, and I started a project to encourage more people to plant Aristolochia. Two years ago, I purchased about 100 tiny seedlings from the UC Botanical Garden plant sale (great sale, by the way) and distributed them locally to neighbors and other interested parties.
This effort had a high rate of failure: many people simply didn’t water the tiny plants enough, and the deer may have tasted some.
After about four years my own vines are growing well, but even after rearing and releasing swallowtails in my garden, the butterflies have not laid eggs.
We are focusing now on planting Aristolochia in appropriate riparian parks, working with the City of Oakland Stewardship Department and the East Bay Regional Park District. We have enlisted volunteer stewards who will keep an eye on the plants when they are young.
But the difficulty with this project has been the long-term commitment it requires to grow the vine with no promise of seeing butterflies. Nevertheless, I keep an eye on the Aristolochia vines I steward, hoping someday to find eggs and to once again see that spectacular blue butterfly.
Notes from the Editor:
Here are a few things to know about attracting pipevine swallowtails to your garden.
- Not only do pipevine swallowtail caterpillars need Aristolochia, but the adult butterflies need nectar-producing flowers to fuel their flight. Butterflies are mostly generalists when it comes to nectar, but creating groupings of the same nectar plants will keep them in your garden longer. Try to include locally native plant species; they have co-evolved with local butterflies and provide the best habitat. You can find lists of butterfly plants for the Bay Area on the websites of Native Here Nursery, Friends of the Regional Parks Botanic Garden, and Yerba Buena Nursery.
- Avoid using pesticides at all costs. Even the “natural” bacterial insecticide BT (Bacillus thuringiensis) kills butterfly larvae.
- Relocating caterpillars or rearing them in captivity may not be a successful strategy. Instead, focus on creating habitat that supports both caterpillars and adults—and cultivating patience. Art Shapiro, entomologist and professor of Evolution and Ecology at UC Davis, suggests an approach on his website:
Few butterfly species can maintain an ongoing population within the confines of a residential lot—even a big one. If you get breeding, it will be as part of a larger “metapopulation” whose borders are constantly changing. Remember that an ongoing population requires larval host plants, pupation sites, adult food supply, and mating sites (which often means territories for males). Or just plain good juju.