Sonoma Botanical Garden to unveil colorful citrus exhibition

After more than a year of extensive planning that required a deep dive into the international citrus scene, Sonoma Botanical Garden will unveil its first-ever indoor exhibition on Saturday.

“From East to Zest: Citrus’ Colorful Journey Across the Globe,” featuring a diverse array of colorful plants from throughout the world, will be in the greenhouse of the garden, formerly known as Quarryhill Botanical Garden, at 12841 Highway 12 in Glen Ellen. The California Oaks Trail, which provides an easily accessible route to SBG’s acclaimed Asian garden, will open the same day.

“Visitors can enjoy a squeeze of color this winter as the garden transforms its greenhouse into a cornucopia of living citrus trees in fruit,” said Kate Rabuck, director of visitor experience. “Immersed in fragrance and color, visitors can learn fun facts as they stroll, from the myth of the Meyer lemon to the cause of the grapefruit effect.”

The myth of the Meyer lemon centers on this fruit not being a lemon at all, but instead a cross between citron and some form of orange. The grapefruit effect refers to how naringin, one of the chemicals found mostly in the fruit’s peel, pith and membranes, can impair the body’s ability to absorb certain medications.

Executive Director Scot Medbury came up with the idea of an exhibition focusing on citrus, but bringing his vision to fruition required a concerted team effort.

“Virtually all citrus originated in East Asia, and given the garden’s history with Asian flora, it was thematically appropriate for us to branch out into what happens when humans intervene in the evolution and migration of plants,” Rabuck said.

The garden already had one wild citrus specimen in the collection, but its fruits are extremely bitter and virtually inedible, so the exhibition focuses on how humans have taken wild plants and bred, cultivated and hybridized them over generations to better fit our tastes.

“Plus, who doesn’t love a big squeeze of color during the sometimes-dreary winter season?” Rabuck added.

A proposal to create the exhibition was first discussed in 2020, but the pandemic delayed plans. Garden staff members began putting the exhibition together last winter by seeing if a few trees would thrive in the greenhouse space and monitoring when they would flower or fruit so that the most impactful experience could be offered to visitors.

“There are very few species of citrus that thrive outdoors in Sonoma County year-round,” Rabuck said. “A greenhouse has a very different set of growing conditions that can be great when cold is the issue, but it also comes with a different set of horticultural challenges. Fortunately, the test trees were a success through the winter, so the acquisition of interesting cultivars and forms began.”

Nearly all plants in the exhibition are newly acquired; about one-third are on loan from partners and will be returned after the exhibition ends on March 5, while many others will be planted around buildings and become part of the garden’s permanent collection.

California has strict rules about bringing citrus in and out of quarantine zones, so the staff had to be sure that the citrus plants they brought to the exhibition would not spread diseases or pests.

“We actually had a nursery partner in a different zone who was willing to loan us some fantastic trees, but we had to turn them down out of an abundance of caution,” Rabuck said.

Eventually, more than 60 trees from several nurseries, including Sonoma Valley Wholesale Nursery, were collected.

She says that although “native” is a tricky term when referring to cultivated species, it is generally accepted that all modern-day citruses originate from five ancestral species that are native to Southeast Asia.

“We have samples of almost all of them,” she said. “Most of the citrus you see in cultivation today, including those in the exhibition, have been intentionally and accidentally bred and hybridized over generations to produce the huge diversity of citrus fruit we know and love. Because there was human intervention in their evolution and cultivation, they aren’t really considered native to anywhere.”

The exhibition will open to the public on Saturday and can be accessed by anyone who pays the garden admission fee ($12 for adults, $10 for senior 65 and over, and $10 for military personnel and students). Members and children 12 years old and younger are admitted free.

Alan Porter, a volunteer who helped to research the exhibition, will lead a monthly guided tour, focusing on the evolution of food. The tour will first be offered on Nov. 17 at 10 a.m. and costs $7 for members and $19 for nonmembers.

Visitors who also want to experience the garden’s Asian woodland area should plan to stay an extra hour or two, Rabuck said. The garden was founded on a love for biodiversity as well as an appreciation for plants from temperate parts of East Asia.

The exhibition is seen as a pilot project in helping the garden achieve its mission: to inspire an appreciation and understanding of the beauty and value of Asian and California native plants, and promote their conservation in natural habitats and gardens.

“If the exhibition is successful, we will likely do similar botanical exhibitions in the future,” Rabuck said. “With a limited budget and small staff, we are very careful about making sure our efforts are being deployed in ways that best fit our mission.”

Reach the reporter, Dan Johnson, at daniel.johnson@sonomanews.com.