It is my fervent wish to enhance and preserve the Hallberg Butterfly Gardens so that future generations will always have the opportunity to behold the beauty of nature’s wonderful miracle—the butterfly.
Located on nine acres in the rolling hills of West Sonoma County, the Hallberg Butterfly Gardens may be the oldest butterfly garden in the country. Situated twelve miles inland from the Pacific Ocean, the climate provides hot summer days and cool nights when the marine air rolls in. This is the same area that Luther Burbank chose as the “perfect climate” for his experimental farm and gardens; Sunset would place it in zone 15.
Louise Hallberg’s grandparents and parents farmed the property with apples, pears and berries. Louise, now in her eighties, was born here and has lived all her life in the family home. It is a modest Queen Anne style house built in 1883, set in a garden planted in the 1920s by Della Hallberg, Louise’s mother. Mature camelias, rhododendrons, magnolias, palms, wisteria, azaleas, and flowering quince surround the house, creating a sheltered “jungle” habitat for birds. A stately 150-year-old black oak (Quercus kelloggii), recognized as a heritage tree in Sonoma County, provides a canopy over the house.
Della also planted California Dutchman’s pipevine (Aristolochia californica), a slow growing native vine that happens to be the only host plant for the larvae of the large, beautiful, black-and-teal pipevine swallowtail (Battus philenor-linnaeus). Now, eighty years later, the plant can be seen climbing through the nectar and larval food plants that feed other species of butterflies. Though the vines are extensive, they blend into the background without visually overwhelming the garden.
It was the resulting profusion of pipevine swallowtail butterflies from this early planting that sparked Louise’s interest. She realized that she had something special that she wanted to pass on to others. She invited classes from the local school (the school that she herself had attended) to tour her garden. Those first tours were more than twenty years ago. In 2001, over 1300 children from all over the county visited the gardens.
Life Cycle of a Butterfly
Understanding the four stages in the life cycle of a butterfly is key to appreciating this garden. Eggs are laid on the leaves or stems of a host plant; some butterfly species lay only on one kind of plant while others lay on a variety of hosts. Each egg hatches into larva (a caterpillar) that begins to feed voraciously on the host plant. The growing caterpillar sheds its skin several times, then attaches itself to a twig or other object, and forms a pupa (a chrysalis). In a miraculous transformation, a butterfly emerges some time later, feeds on nectar, mates, and continues the cycle by laying eggs.
Louise realized early on that to provide a proper habitat for butterflies in a garden requires plants that meet the needs of each stage in a butterfly’s life. The larval host plants are particularly important, although they are often the least showy in the garden. And there needs to be plenty of each of the host plants to maintain populations of specific butterflies. The plants that provide food for the adults are more diverse—and often more showy; most butterflies will feed on any flower that offers both nectar and a broad platform for them to land on in order to access the nectar.
Besides providing plants for both larvae and adults to feed on, a safe habitat or shelter is also important. For this reason, grooming here is done only when absolutely necessary, at times giving the garden a somewhat overgrown appearance. All weeding is done judiciously by hand. Pruning is delayed until spring to give as much time as possible for the chrysalises to hatch. Damp soil and mud puddles are a vital source of water and minerals for the butterflies.
While no pesticides are used in the garden, there is concern about the effects of such chemicals used in the surrounding agricultural areas where apples and grapes are grown. Even biological controls, such as those for coddling moths on apple and various caterpillars on vegetables, threaten butterflies.
Some areas of the garden are favored by butterflies more than others. In spring, the first butterflies are seen in an area at the top of the hill, flanked by the house and thick shrubbery to the north, the barn to the east, and thick shrubbery and trees to the west. It is usually warm and calm in this area. A large perennial wallflower (Erysimum ‘Bowles Mauve’) provides nectar early and throughout most of the year. Butterflies abound on this plant, as they do on an orange butterfly bush (Buddleia globosa) which flowers early in this protected spot; visitors enjoy the honey scent from it.
The pond area is planted in a cottage garden style, dense with flowers. Many of the plants in this area are larval food plants: various milkweeds (Asclepias spp.), lavatera, sildacea, penstemon, bronze fennel, yarrows (Achillea spp.), diascia, snapdragons, and a number of ornamental grasses. In the background are California lilacs (Ceanothus spp.), madrone (Arbutus menziesii), coffeeberry (Rhamnus californica) and several willows (Salix spp.)—all larval food plants. Hidden behind the flowers, and away from visitors’ hands, is a patch of stinging nettle (Urtica dioica). Louise never saw red admiral butterflies (Vanessa atalanta) in her garden until she planted the nettles; a folded leaf usually indicates that a red admiral or a painted lady caterpillar is tucked inside.
Louise’s passion is not just in attracting colorful and varied butterflies to her garden but in creating a garden where all species will visit, lay their eggs, and, in turn, reproduce many more butterflies. In her tours of the garden, she shows people the eggs on the host plants, the caterpillars feeding on foliage, and the chrysalises. Many visitors to the garden express dismay when they realize that they have killed the caterpillars of butterflies they find so magical. However, visitors expecting to see a profusion of butterflies, such as those seen in theme park enclosures, will be disappointed here; this is an informal garden, in a natural and agricultural setting, that attracts naturally occurring populations of butterflies.
Observing and Recording
Since 1986, Louise has kept meticulous daily records of her observations of the pipevine swallowtail. Since 1992, she has recorded all other butterflies seen and their frequency. Regular butterfly visitors to her garden, in addition to the pipevine swallowtail, include the anise and western swallowtails (Papilio zelicaon and P. rutulus), the monarch (Danaus plexippus), various skippers, echo blues (Celastrina ladon subsp. echo), and, of course, the cabbage white (Artogeia rapae). Seen but rarely are the great purple hairstreak (Atlides halesus), the crown fritillary (Speyeria coronis), and the common buckeye (Junonia coenia).
This location has been an official Federal weather station for the Sebastopol area since 1968. Because day to day variations in weather can affect the numbers of butterflies seen, these records add a further dimension to the butterfly observations. Just what effect seasonal variations in the weather have on butterfly populations is not well known at this time. The anise swallowtail has appeared at the same time each year, in spite of the year to year differences in weather. However, it is likely that loss of habitat has the greatest impact on variations in butterfly populations.
Predators of eggs and caterpillars are numerous; birds, yellow jackets, spiders, and other insects take their toll. Louise takes many eggs, caterpillars, and chrysalises to be raised in the safety of her home. If the weather is not suitable for releasing the newly hatched butterflies into the garden, she hand feeds them until conditions improve.
In 1997, Hallberg Butterfly Gardens were incorporated as a 501(c)(3) non-profit organization, in the hope of preserving this sanctuary for future generations of both butterflies and people.