June 2022

by Tony Gurnoe, Director of Conservation Horticulture

The San Diego Botanic Garden is playing a key role in the global conservation of oak trees (Quercus L.). San Diego Botanic Garden’s Conservation Horticulture staff have been working to conserve endangered native oak species, both in habitat and in cultivation since the beginning of the Garden’s Science and Conservation department. Notable examples of the impact SDBG has had on regionally native endangered species of Quercus include cultivating the first ex situ conservation accessions of Cedros Island oaks (Quercus cedrosensis) from acorns collected within the small and highly threatened U.S. population of that species. SDBG has since begun distributing those plants to partnering botanical gardens as an additional safeguard, while continuing to monitor and propagate from plants in the Otay Mountain Wilderness area immediately north of the U.S. border with Mexico. Another example of early successes of SDBG’s oak conservation program includes the Garden working in partnership with the City of Encinitas to establish a new occurrence of the endangered Nuttall’s scrub oak (Quercus dumosa) from data rich plants grown from locally collected acorns within the Cottonwood Creek Park restoration site. These plants are among the first endangered oaks within a municipally managed landscape to be tracked as part of a broader conservation metacollection anywhere in the world. SDBG staff also collaborated with the City of Encinitas to install more than 4 dozen native trees within a local park for Arbor Day 2022, including coast live oaks (Quercus agrifolia) and a rare Engelmann oak (Quercus engelmannii).

The Garden has continued to build upon this capacity to positively impact threatened species of oaks from the southwestern U.S. and northern Mexico. Conservation Horticulture staff have completed field surveys of native oak species in five U.S. states, along with Baja California. The Garden’s living oak collection has grown significantly in importance due to the addition of such rare plants as island oaks (Quercus tomentella) gathered as acorns on Santa Rosa Island, and forward looking climate adapted species from southern Arizona including Toumey oak (Quercus toumeyi). SDBG’s success in building both capacity for impact and botanical expertise related to oak conservation has gained the Garden an important new distinction within the oak conservation community. The Global Conservation Consortium for Oaks (GCCO), which serves as the international coordinating agency for all oak conservation activities, has just recognized the important work being done at SDBG by designating the garden as Species Stewards on behalf of the GCCO for a handful of threatened Californian oak species. Species Stewards agree to work with oaks of conservation significance at a high standard of data collection and integrity, with significant involvement in collaborative conservation planning, and in a way that actively engages with and contributes to ongoing research related to these species. The oaks under SDBG’s stewardship as part of this international conservation program include Quercus cedrosensis, Q. dumosa, Q. tomentella, Palmer’s oak (Q. palmeri), island scrub oak (Q. pacifica), and Q. engelmannii. While some of these projects are too early in their development for visitors to the garden to bear witness to the plants themselves within the botanical garden exhibits, we hope that you’ll visit the Quercus engelmannii within our California Gardenscapes and the Q. tomentella on the ocean side of our new Cork Oak Cafe with a gained appreciation for both how important these trees are, and how important the Garden is to these species.

“As GCCO Species Stewards of Californian oaks, SDBG is able to contribute to scientifically informed conservation action plans for threatened Quercus species from our region leveraging the Garden’s unique talents and expertise, but with a much broader and deeper impact than any institution could have alone.” – Tony Gurnoe