Natural Habitat Restoration at San Diego Botanic Garden
San Diego Botanic Garden is fortunate to include two natural areas within its grounds. Both areas contain species from the rare Coastal Sage Scrub and Southern Maritime Chaparral plant communities, including the endangered Del Mar Manzanita. The Garden has been active in preserving these natural areas by replanting with native species as well as removing invasive plants. A generous grant from San Diego Gas & Electric has funded materials and staff time for these restoration efforts. With the grant, the Garden has added nursery benches for native plant germination studies and will be purchasing a stereomicroscope. As a member of the Center for Plant Conservation, the Garden is participating in a collaborative effort to bank seeds of endangered California native plants. Impacts from development and potential effects from climate change are increasing pressures on vulnerable species. By collecting and preserving seeds of these rare plants, we are safeguarding their future. The correct identification of a species is vital to this program. A stereomicroscope will greatly aid staff with plant identification and seed sorting.
The grant will also allow the Garden to purchase new signs describing our restoration efforts and the importance of preserving the native flora. These will be placed on our Overlook Natural Area boardwalk later in the spring. From the boardwalk, visitors will notice orange flags scattered out in the habitat. These mark where young plants were placed in late winter/early spring. The flags represent six different species, each from seed collected from plants growing in the natural area. Many plant species from this natural community will germinate only under specific conditions, such as after a fire. While lighting a fire in our natural area is not possible, we can mimic the process by burning over our seeds in flats in the nursery. Heat from a fire can crack the seed coat, allowing moisture from winter rains to enter the seed and trigger germination. Fire can also clear the canopy allowing more light to reach the soil and triggering germination for some species. Garden staff have been conducting numerous germination trials to determine which treatments give the best rate of germination for each species. Even with the correct conditions, it is a lengthy process to grow a seedling to a size where it can be planted, most of the young plants put out early this year are over a year old. This past fall, the Garden has been successful in germinating a number of Del Mar Manzanita and Warty Stem Ceanothus, another threatened species, which we hope to plant out this coming winter.
Another important aspect of native habitat conservation is the removal of invasive plants. Invasive plants use up precious resources, shade out native species and, in some cases, alter soil chemistry, making it no longer suitable for native plants. By removing these invaders, we are giving our seedlings a better chance to thrive, as well as maintaining a healthier existing native plant community. These efforts towards preserving endangered species and expanding our environmental education program are possible thanks to San Diego Gas and Electric’s generous 2013 Environmental Champions grant to San Diego Botanic Garden.