by Tony Gurnoe, Director of Horticulture
Sunsets are coming earlier and mornings are once again laden with dew here in Encinitas. Respite from long, hot summer days, prospects of rain, and the residual warmth held in the earth make this a perfect time to plant native species. California is home to more than 6,500 taxa of native plants, more diversity than any other state. The San Diego Botanic Garden sits in the heart of one of only 25 internationally recognized biodiversity hotspots. This incredible plant palette allows us to create landscapes unlike those found anywhere else in the world. However, such privilege comes with significant responsibility.
More than 40% of California’s plants are endemic, meaning they do not naturally grow anywhere else, and more than one third are considered rare or endangered. San Diego has the most endemic or endangered plants of any county in the country, and without our help many of them will disappear within our lifetime. I don’t mean to scare or distress you, but to help you understand just how special and imperiled California’s plants are. Several months ago I spoke before the California Native Plant Society (CNPS) at their Conservation Conference about the San Diego Botanic Garden’s plans to dramatically increase our native plant conservation efforts and programs. Among the rarest native plants in our garden you’ll find Nevin’s Barberry (Mahonia nevinii), Tecate Cypress (Hesperocyparis forbesii), and of course the Del Mar Manzanita (Arctostaphylos glandulosa ssp. crassifolia), but the focus of my presentation was our ambitions regarding Orcutt’s Hazardia (Hazardia orcuttii). This mild mannered shrub is down to one remaining population of a few hundred plants in the entire United States.
The San Diego Botanic Garden partnered with the California Department of Fish and Wildlife (CDFW) for an Orcutt’s Hazardia reintroduction project. Thirty individuals were planted in a small plot of clay soil within one of our native plant preserves. Most of those plants are still alive, but more than a decade later not a single seedling has emerged successfully. Late in the summer of 2017, San Diego Botanic Garden staff and volunteers decided to stand up for this species rather than watch it slowly slip into extinction.
My team began monitoring our living collection for environmental stressors, flower bud production, and eventually seed production. In November of 2017, we collected and cleaned seed from 16 mother plants. Previous nursery trials yielded germination rates as low as 6%, so it was a wonderful surprise that we broke 75% germination on our first attempt. More than 150 individuals of Hazardia orcuttii are now blooming merrily in our nursery. We’re coordinating with the CDFW and local partners to find the most advantageous home for these rare specimens.
Our immense pride in the fighting chance that we’ve offered Hazardia orcutti is tempered by the realization that this is just one among thousands of threatened species of California natives. Fortunately this is also just the beginning of the San Diego Botanic Garden’s ex-situ native plant conservation work. With our new leadership, new facilities, and your continued support, I’m confident that we’ll preserve the plants that make California so special for generations to come.