Waiting for the Big Blue Butterfly

I can still remember exactly where I was when I encountered a pipevine swallowtail for the first time. My husband and I were walking along East Ridge Trail in Redwood Regional Park when an extraordinary blue butterfly drifted past us. It was surprisingly large, measuring roughly five inches from wingtip to wingtip, and I had never seen a butterfly with such an intense, shimmering blue color. It looked almost tropical and completely out of place in the landscape. We followed it for a while, wondering aloud, “What was that?” until it vanished among the trees.

I soon discovered that this butterfly is named after the only genus of host plant its caterpillars depend on: pipevine, or Aristolochia. California has only one native Aristolochia species, California pipevine (Aristolochia californica). Although this plant is highly poisonous, it is the sole food source for pipevine swallowtail caterpillars. It naturally occurs in riparian areas and forests in Contra Costa County and parts of Alameda County. Elsewhere in the southern United States, pipevine swallowtails occur across a much broader area, where their larvae feed on other species of Aristolochia.

A Butterfly That Captured Public Attention

I was far from the first person to become fascinated by this remarkable butterfly. A CBS News report about biologist Tim Wong generated considerable interest in pipevine swallowtails. Wong raised the butterflies in a protected greenhouse in his backyard, where he cultivated Aristolochia. He later released the butterflies at the San Francisco Botanical Garden, where he had originally obtained cuttings of the vine.

Jim Spinello of Alamo was among the people inspired by that news report. An experienced butterfly keeper, Spinello had already noticed pipevine swallowtails passing through his yard, so he decided to grow Aristolochia himself. Just one year after planting the vine, he discovered eggs on it.

However, this should not be taken as a typical result. Most gardeners who plant Aristolochia will not encounter pipevine swallowtails for several years, and some may never see them at all. Spinello happened to live along an established route or flyway used by an existing butterfly population.

Growing the California Pipevine

The host plant itself requires patience. Aristolochia can take several years to become firmly established and even longer before it reaches a size capable of supporting a colony of pipevine swallowtails. Once mature, however, it can become enormous, producing vines as long as 20 feet that spread across the ground or climb into trees. Because of its size, it is not an easy choice for many Bay Area gardens.

Although California pipevine is often associated with riparian environments, it can grow successfully in gardens that do not have a stream nearby. The important requirement is sufficient watering while the plant is becoming established. Experts generally recommend placing the roots in shade while giving the growing vines access to sunlight.

During Spinello’s first year, his young vine was still too small to provide enough food for the caterpillars that arrived. He therefore had to locate additional Aristolochia plants to feed them. In doing so, he began connecting with other people who were also cultivating the vine.

Raising Pipevine Swallowtail Caterpillars

The following year, Spinello ended up with so many larvae that he could no longer raise them all himself. He began distributing them to other gardeners, whom he jokingly refers to as “caterpillar-sitters.”

That year, he placed approximately 300 larvae with foster caretakers and had another 200 developing inside chrysalises. The butterflies would remain in this overwintering stage until emerging the following year. For many first-time caterpillar-sitters, the long wait can be surprising, especially when they realize that “next year” really does mean next year.

Terry Smith and the Pollinator Posse

The lengthy process did not discourage Terry Smith, a retired science teacher and one of the co-founders of the Pollinator Posse. This nonprofit organization encourages gardeners to create environmentally friendly landscapes that provide resources for pollinators.

Smith planted California pipevine in Piedmont eight years ago. Through the Pollinator Posse network, she became one of the people who helped care for pipevine swallowtail larvae. Even with the connections and experience available through the group, it took her two years to achieve success. Eventually, she discovered between 200 and 300 eggs on her vines.

Like Spinello, Smith quickly found that her plants could not support every caterpillar on their own. She therefore had to locate other gardeners willing to act as caterpillar-sitters and help provide food for the growing larvae.

Rising Demand for California Pipevine

Pete Veilleux, owner of East Bay Wilds Native Plant Nursery in Oakland, has noticed a dramatic increase in interest in Aristolochia. Demand has grown so much that keeping the plant available has become difficult. He estimated that he sold approximately 2,000 plants during the previous year, with most buyers specifically hoping to attract pipevine swallowtails.

According to Veilleux, wild California pipevine performs particularly well on moist slopes facing north or east, especially along the margins of wooded areas. Road cuts can provide favorable conditions because they allow the vines to receive sunlight during either the morning or afternoon.

Veilleux propagates his plants from cuttings. He agrees that the species can be slow to establish, but says regular, generous watering can accelerate its growth. He also notes that the vines can be trained along fences, particularly chain-link fences, which makes them more practical for residential gardens.

Flowers and New Growth

California pipevine produces flowers and fresh leaves in March. As the plant develops, its long vines can spread widely or climb into nearby structures and vegetation.

Its growth habit and size are important considerations for anyone thinking about planting it specifically for pipevine swallowtails. The plant may eventually provide an abundant food source for caterpillars, but reaching that stage requires considerable time and care.

My Own Experience With California Pipevine

Before becoming too enthusiastic about planting Aristolochia californica, it is important to acknowledge that my own experience has been far from completely successful.

Through the Pollinator Posse, Terry Smith, entomologist Eddie Dunbar, and I began a project intended to encourage more people to cultivate Aristolochia. Two years ago, I purchased roughly 100 very small seedlings at a plant sale held by the UC Botanical Garden and distributed them among neighbors and other people interested in supporting the project.

Unfortunately, the survival rate was poor. Many recipients simply did not provide the tiny plants with enough water, while deer may also have sampled some of them.

After approximately four years, my own vines are now growing well. However, despite raising pipevine swallowtails and releasing them in my garden, I still have not found any eggs deposited on my plants.

Planting Pipevine in Suitable Habitats

Our current focus has shifted toward establishing Aristolochia in appropriate riparian parks. We are working with the City of Oakland Stewardship Department and the East Bay Regional Park District to identify suitable locations.

Volunteer stewards have also been recruited to monitor the plants while they are young and vulnerable. Their involvement is important because newly planted vines require attention and care before they become established enough to thrive on their own.

The Long Wait for a Butterfly

The biggest challenge of this project is the long-term commitment it demands. Growing California pipevine successfully takes years, and there is no guarantee that pipevine swallowtails will eventually appear and lay eggs.

Even so, I continue checking the Aristolochia vines under my care. I remain hopeful that one day I will discover pipevine swallowtail eggs among the leaves and once again have the chance to watch that spectacular blue butterfly moving through the garden.