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Friends of the Regional Parks Botanic Garden
Native Plant Sales
every Thursday morning from 9 to 11 AM
at the Juniper Lodge
October 2011


The Pipevine Connection

Editor's note: Bert Johnson is retiring in October after a long career as gardener at the Regional Parks Botanic Garden. I asked him to write a piece on a topic of his choosing as sort of a farewell to the garden. It is typical of Bert that his thoughts turned to a California native plant.
The California pipevine (Aristolochia californica, also called Dutchman's pipe) has become one of our more popular native vines for use in our gardens. It is entirely endemic to California. Though widespread, it is actually not common. Its occurrences are widely disjunct, and it is generally sparse wherever it is found. Dutchman’s pipe chiefly occurs in the foothill woodland belt, often where mixed oak woodlands occur. The plant can be found in our North Coast ranges, the foothills bordering the Sacramento Valley, the foothills of the northern and central Sierra Nevada, some of the hills around the San Francisco Bay region, and in the Santa Cruz-Monterey region of our central coast. Some closer-to-home locations for the plant in our bay region include Lake Merced (along Brotherhood Way) in San Francisco, Briones Regional Park in our East Bay hills, and in both Rockville Hills Regional Park and King Ranch in Solano County. The plant also occurs along the American River east of Sacramento. I find it odd that the plant does not occur on Mount Diablo, as I expect it would be there.
Aristolochia californica is often found in riparian habitats near creeks on shaded wooded slopes or flats of stream banks. The plant mostly grows like a groundcover in both Buckeye Canyon of Briones Regional Park and along Las Trampas Creek in Lafayette, as was shown and shared with me by plant wizard Glen Schneider of Berkeley. About thirty years ago, I also discovered Dutchman’s pipe covering a sizable area of grassland in a “seepy” slope south of Sindicich Lagoon in Briones Regional Park. The plants at King Ranch in Solano County also sprawl along the ground. So Dutchman’s pipe will often assume a groundcover growth habit. When doing so, it seems to rarely produce flowers. But when the plant climbs and twines itself above ground on other supporting shrubs or fence lines such as in our botanic garden, it blooms profusely year after year. At Rockville Hills Regional Park in Solano County, the pipevine twines itself up the trunks of toyon and blooms prolifically. In our botanic garden, the plants that assume the habit of a groundcover do not bloom, while plants that climb on other plants or fences do consistently bloom. In addition, plants that climb usually produce fruits, while plants that creep usually do not bear fruit. I believe that sufficient light may be one factor in the production of fruit on Dutchman’s pipe.
Aristolochia californica

Aristolochia is a genus of about 500 species and is generally found in tropical or warm temperate regions. There is only one other native plant member of the pipevine family (Aristolochiaceae) in California--our wild ginger (Asarum). There are actually four species of wild ginger in California.  The more common species is Asarum caudatum, which grows as a groundcover in the more mesic regions of our coastal redwood forest. Asarum has heart-shaped leaves and bears purplish or maroonish flowers. These foliage and flower features are similar to those of Dutchman’s pipe. However, Dutchman’s pipe flowers are very distinctive and greatly resemble the meerschaum pipe smoked by Sherlock Holmes. The flowers of Dutchman’s Pipe also resemble the plump little marshmallow “chickens” or “peeps” that are such popular treats during Easter.

The flowers of Aristolochia differ in their size, shape, and color depending on location. The flowers can be larger or smaller or narrower or broader in their inflated appearance. The flowers are extremely ornamental, having a tropical appearance and somewhat resembling those of the insectivorous pitcher plant. The flowers are usually a fleshy color with purplish stripes or may instead be a more yellow-green color. The usually fleshy color and purplish markings of the pipevine flower may mimic carrion colors and may also serve to attract the plant’s small, fly-like insect pollinators called fungus gnats. These tiny gnats enter and remain inside the flower for a duration of time unknown to me. But they are easily freed from their imprisonment chamber and provoked to escape and fly away when a person chooses to tear open a flower and release them. Flowers are borne loosely and uncrowded along the stem of the twining vine. In their loose and dangling arrangement along the vine, they bring the image of dangling clusters of string beans  to mind.

Pipevine Swallowtail (Battus philenor)
As curious as the flowers are, their charm is rivaled and perhaps even surpassed by the shiny black pipevine swallowtail butterflies harbored by this plant. More attractive than the females are the males, which are colored a deep black with almost iridescent blue or turquoise markings on their wings. The females are instead a duller charcoal-black with brownish markings. Aristolochia californica is the only food plant used by the larvae (caterpillars) of the pipevine swallowtail. Without this plant, these butterflies would not exist or reproduce. As the caterpillars feed on the plant, they ingest and store toxins from the plant in their bodies, which makes them poisonous and unpalatable to predators. These toxins are present in the body of both the caterpillar larva and the adult butterfly. Since the toxins are both distasteful and poisonous to predators, pipevine swallowtail caterpillars and butterflies remain mostly unbothered by most birds and other potential predators. Our popular monarch butterfly also ingests and accumulates a toxin in its body from the milkweed it feeds upon, which also effectively deters predators.
The life cycle and “connection” between the pipevine plant and the pipevine swallowtail is utterly fascinating. The pipevine plant becomes deciduous and is therefore leafless during the winter. In late winter or early spring, usually in mid to late February but sometimes later in March, the plant begins to produce its flowers on the naked and leafless stems. As the fleshy-colored flowers later begin to fade, the newly developing “fuzzy” and heart-shaped leaves emerge. During the time that the leaves begin to develop and mature, the female pipevine swalllowtail butterfly will lay her eggs on either leaves or stems, usually in the outermost tip region of actively growing stems. The small, orangish eggs are often laid in clutches of 13 in California (Fordyce, J. A., “Between-clutch interactions affect a benefit of group feeding for pipevine swallowtail larvae”, Ecological Entomology (2006) 31: pp.75-83.)
As the young caterpillars emerge from the eggs, they first feed on the eggs and leave half-eaten egg shells behind. These tiny caterpillars are either blackish or a somewhat reddish plum color. They prefer to feed on only the new young leaves that grow nearer to the outer tips of twining stems, so they don’t need to stray very far from their birthplace. The juvenile caterpillars will often congregate and gather in what are called “groups” or “gangs”. When feeding, these young caterpillars usually congregate into clusters or rows that often resemble a bunch of miniature parked buses. These “gangs” will often join other gangs or “clutches” of young caterpillars and form a communal feeding party. Gang fights are not an issue with these caterpillars.
Pipevine Swallowtail larva

Pipevine Swallowtail Chrysalis

As the caterpillars feed together, usually along the edge of a leaf, they grow quickly, molt, and shed their skin. They do this five times, and each molt is called an instar. During each instar, the larva will consume its own skin. Now that’s what I call being “green”. Each molt or instar produces a larger caterpillar as well as increasing toxicity of the caterpillar’s defense against predators. During the earlier instars, when the smaller caterpillars are less toxic, they are apparently more vulnerable to predators. Thus, it is certainly to the advantage of the caterpillars to feed and grow quickly to increase both their size and concentration of toxins to discourage predators. After about the fourth instar, the caterpillars become more solitary in their feeding. At this time, they feed on both leaves and fruits of the plant. In the botanic garden during the late summer of 2007 and 2008, it was amazing to watch many of the larger caterpillars voraciously eating and leaving behind many half-eaten banana-like fruits. The fruits are said to be even more concentrated in their toxins than the leaves. During the fifth and final instar, the caterpillars become fully mature and are usually two or so inches long and slightly thicker than a pencil. The caterpillars are shiny black with orangish spines or more rarely a plum color with yellow spines. The caterpillar finds a place to attach itself and then pupate. The pupae greatly resemble  miniature Egyptian mummies. They are either tannish, brownish, or a very striking and beautiful iridescent lime green color.

During early April of 2011, Maggie Ingalls and Janet Mackey escorted me to King Ranch in Solano County, where the pipevine plant and swallowtails occur. There, some of the male butterflies instead display an unusual greenish-blue color on their wings, which I had never before seen. The males were showing off and “hill-topping” on the ridge top, cruising for females to attract. On this day, the usual and persistent Suisun winds were gusting violently, and the butterflies were being tossed around like delicate pieces of paper. The butterflies would eventually rest and find shelter on the leaves of nearby coast live oaks. It was then that I was able to capture still photos of them. There were in total only about a half dozen or so butterflies here. When in flight, pipevine swallowtails have a choppy and erratic “up and down” and “back and forth” flight pattern much resembling a staggering drunk. By comparison, both the anise and tiger swallowtails exhibit a smooth and even gliding flight pattern. The pipevine swallowtail, like most other species of swallowtail, is often either solitary or occurs in very low numbers.

In the years between 2007 and 2010,  some of which had drier spring seasons, the pipevine swallowtails were actually abundant in the botanic garden, while during the very cool and wet spring of 2011, the pipevines were scarce in the garden. I saw only a few caterpillars and butterflies during 2011. However, during the same year, the pipevine swallowtails that I often see in Benicia Community Park in Benicia were abundant and I witnessed them frequently, particularly during July.  On July 4, the pipevine swalllowtails were abundant and active during the afternoon hours in Benicia Community Park between 1:30 and 4:30 p.m. During this three-hour period, I saw and counted a butterfly about every ten minutes. During much of July and August, the butterfly activity remained strong in this park.  It seems that butterfly activity is always more pronounced on warmer summer days and during the warmer and later afternoon hours. The butterflies witnessed in Benicia Community Park always seemed to be intentionally flying in either a northerly or southerly direction, with a nearly equal count of butterflies going in either direction. Most butterfly sightings were of males, representing about 95% of the sightings. I do not know if these sightings represented individual butterflies or were instead repeat flyers.

I can only surmise that these butterflies seen in Benicia Community Park were arriving from the King Ranch area of the Cordelia Hills not too far north of this park. But where these butterflies actually come from and go to in either direction is still a mystery to me. I do  often witness pipevine swallowtails flying in both Benicia State Recreation Area and Benicia Community Park during the summer months. I also see the butterflies flying across and through the residential areas of Benicia between both parks, so the backyards and homes in Benicia lying between both parks may actually be a designated and historical flight course for these butterflies in their search for both nectar and mates.

During the summer months in both Benicia State Recreation Area and Benicia Community Park, I have noticed that the pipevine swallowtails will often nectar on some of our more obnoxious weeds, notably the yellow star thistle (Centaurea solstitialis), purple star thistle (Centaurea calcitripa), and artichoke thistle (Cynara cardunculus). At Benicia Community Park during July and August, I have also seen them nectar on the weedy purple-flowered Limonium lanatum. I have also noticed pipevine swallowtails and honeybees nectaring on the white clover (Trifolium repens) growing in the lawn areas of Benicia Community Park during the summer months. During the spring season, I have noticed pipevines popularly feeding on blue dicks (Dichelostemma pulchellum), Ithuriel's spear (Tritiellia laxa), and Italian thistle (Carduus pycnocephalus).

There is a real mystery behind the pipevine swallowtail and its food plant. Both are so sporadically encountered in nature. But even more mysterious to me is the question of just how far these butterflies “stray” from their food plant locations in nature. I so often see this butterfly in Benicia and its parks as mentioned, as well as within Crockett Regional Park across the Carquinez Strait from the town of Benicia. Yet its food plant, the Dutchman’s pipe, is often a considerable distance away from where I see the butterflies. In Crockett, the closest population of the Dutchman’s pipe that I know of occurs in Briones Regional Park several miles away. In Benicia, the butterfly’s food plant lies several miles north of town in the Cordelia Hills. Yet quite contrary to this situation, the pipevine swallowtail butterflies in our botanic garden tend to stay in the garden and close to their food plant, even during their mate- and nectar-searching ventures. There is so much more that I need and want to learn about these spectacular butterflies.


--Bert Johnson

Request for Submissions

Have you ever thought that you had something interesting to say about plants?  Perhaps thoughts on a favorite plant, much as Bert Johnson expresses in his article?  A favorite wildflower spot?  A class you took?  This newsletter is a perfect place to dip your toe into the water.  Not much pressure and an appreciative audience--what else do you need?  Who knows?  It may just be the beginning of your writing career.  Send your ideas to John Rusk   .  The two of us may be able to put something together.

Upcoming Classes

A click here will take you to a fuller description of the class as well as the class registration form
October 8 Fall Propagation of California Native Plants Class is full
October 15 Botanizing California: The Varied Faces of Mount Saint Helena Space Available
Five Sundays starting November 6 Ethnobotany: An Introduction Space Available

Illustration/Photo Credits

©Peg Steunenberg Pipevine Plant with Butterfly; all sidebar illustrations
Public Domain--Kaldari Pipevine Swallowtail
Public Domain--Megan McCarty Pipevine Swallowtail larva, Pipevine Swallowtail chrysalis
John Rusk Aristolochia californica