Native Trees: San Francisco’s Long time Residents

April 24, 2017

California is widely known as the home to some of the largest trees in the world. Among them is the native California redwood (Sequoia sempervirens) and native giant sequoia (Sequoiadendron giganteum), the latter species boasting the largest single living tree (by volume) in the world. Here in San Francisco, a unique microclimate, windy conditions, and sandy and serpentine soils have precluded the area from having an extensive native tree canopy, let alone producing the aforementioned “big trees” found in other parts of the state.

 

Nevertheless, San Francisco has always had its share of native trees. Long before the major tree plantings of the late 1800s, small stands of native oaks, bay laurel, willows, and California buckeye graced the landscape, near creeks and in canyons, and in the city’s less windy eastern side. In fact, the coast live oak (pictured left) was among the most important food sources for the Ohlone Indians. Acorns, when ground into meal, provide high protein calories year-round and were important in winter and other times of scarcity. You can also still see some of the area’s early oak trees in remnant patches such as the Oak Woodlands in Golden Gate Park. In San Francisco A Natural History, Garr and Miller (pg. 53) noted, “Arroyo willow thickets lined the former city creeks, along with occasional wax myrtles. California Bay trees or laurels were located along Mission Creek in the Mission District. Coffeeberry (Rhamnus californica) and toyon (Heteromeles arbutifolia), though classified as shrubs, can grow to the size of a small tree.”

 

While today many of the city’s trees are introduced species that have faired well in our unique climate, a number of native trees and shrubs continue to enjoy a place in our landscape. A few notable ones are highlighted here:

 

California Buckeye (Aesculus californica) or California horse chestnut has been called a tree for all seasons. In early spring its bright chartreuse palm-shaped foliage announces spring long before most any other tree. Then in spring and summer it puts on a spectacular display of cone-like white flower spikes. In fall and winter after shedding all its leaves and fruit, its silvery smooth bare branches resemble an ethereal piece of artwork glowing in the moonlight.

 

Aesculus californica is a member of the Sapindaceae (soapberry) family and is the only buckeye species native to California. It is distributed widely in the state among coastal sage scrub, mixed-evergreen forest, riparian areas (rivers & creeks) and central oak woodland. It is a large shrub or tree growing from 13-40 feet tall and is typically multi-trunked. The California buckeye’s crown is as broad as it is high. Young leaves are chartreuse green, turning darker green as it matures and has five to seven palmate (shaped like an open palm or like a hand with the fingers extended) leaflets. It has leathery pear-like seed pods and shiny brown seeds that look like chestnuts. But don’t roast them since they are known to be unpleasant tasting and are toxic.

 

Birds and Bees: The sweetly fragrant flowers of this tree provide a rich pollen and nectar source for native bees, hummingbirds, and many species of butterflies. However, Aesculus californica pollen is known to be hazardous to honey bees, none of which are native to California. It is advised not to plant them near to apiaries.

 

Local native American tribes, including the Pomo, Yokut, and Luiseño, crushed the poisonous nuts to stupefy schools of fish in small streams to make them easier to catch. Buckeye also makes a good fireboard for a bow drill to make fire with.

 

In the garden, California buckeye is drought tolerant. However, it will go deciduous early (summer) if dry, hence, it may look better with some watering. In cool coastal climates, leaves may hold through early fall. Aesculus californica tolerates clay, serpentine, and seasonal flooding. It is also great for a butterfly garden. It works well with other natives such as Buckwheat (Eriogonum sp.), Coffeeberry (Frangula californica), Sticky Monkeyflower (Mimulus aurantiacus), Chokecherry (Prunus virginiana), Oak (Quercus sp.), Redberry (Rhamnus crocea), Currant (Ribes sp.), Hummingbird Sage (Salvia spathacea), Blue-eyed Grass (Sisyrinchium bellum), and many others, as well as numerous annual wildflowers.

 

You can see California buckeye in a number of places in the city, including atop Mt. Sutro in Rotary Meadow. One of the more prominent specimens can be seen on the corner of Willard North and McAllister Street near the University of San Francisco.
 

Hollyleaf cherry (Prunus ilicifollia)

is also known as Islais Cherry. Islais Creek, in San Francisco’s Glen Canyon south of Twin Peaks, is named for the hollyleaf cherry that reportedly grew along this riparian habitat. It is an evergreen shrub to small tree that is native to the chaparral areas of coastal California (from Mendocino County to San Diego County), Baja California, and Baja California Sur, as well as the desert chaparral areas of the Mojave desert. It is a member of the rose family, Rosaceae, and grows 8-30 feet tall with shiny, spiny-toothed leaves. Its fruits are sweet edible cherries, although they contain little flesh. Its small white flowers are produced on racemes (a flower cluster with the separate flowers attached by short equal stalks at equal distances along a central stem) in the spring.

 

Birds and Bees: Hollyleaf cherry is an excellent tree for encouraging wildlife into the garden. The flowers attract bees. The fruits are relished by many bird species and the seeds are consumed by small mammals. These birds and animals also help to disperse the seeds away from the parent plant. In addition, many bird and animal species use the plants for cover as well as nesting places.

 

Native American uses: Central and southern California tribes prized hollyleaf cherry not so much for its minimal fleshy fruit, but for its seed kernel or pit, which had to be subjected to a lengthy cooking process to remove the poisonous hydrocyanic acid it contained. The flour made from the processed pits was said to taste like beans or chestnuts. The Diegueño and the Cahuilla are among the tribes that treated colds and coughs with infusions made from hollyleaf cherry bark and roots.

 

In the garden hollyleaf cherry is easy to care for, has a low water requirement, and tolerates a variety of soil. It can tolerate temperatures down to 15° F. It works well with native trees and brush such as Coyotebrush (Baccharis pilularis), Barberry (Berberis sp.), Ceanothus sp., Redbud (Cercis occidentalis), Toyon (Heteromeles arbutifolia), Pines (Pinus sp.), Oak (Quercus sp.), Flannelbush (Fremontodendron sp.), Currant (Ribes sp.), and many others. It is deer resistant, and can be used as a hedge or for bank stabilization.

 

 

Come Visit Us!

The Sutro Stewards Native Plant Nursery is a great place to learn about native plants. To learn more about the nursery and our Wednesday volunteer opportunities, see our Nursery page. To learn about Sutro Stewards’ other activities and volunteer efforts see our Events calendar.

 

 

 

 

References

 

  1. Sequoiadendron giganteum. Wikipedia. March 2017. https://en.wikipedia.org/wiki/Sequoiadendron_giganteum

  2. San Francisco Urban Forest Plan. Final Fall 2014., http://default.sfplanning.org/plans-and-programs/planning-for-the-city/urban-forest-plan/Urban_Forest_Plan_Final-092314WEB.pdf

  3. Holloran, Pete, Coast Live Oaks (Quercus agrifolica). Historical Essay. Shaping San Francisco’s Digital Archive@FoundSF. FoundSF.org. http://www.foundsf.org/index.php?title=Coast_Live_Oaks_(Quercus_agrifolia)

  4. Garr G. and Miller R. San Francisco A Natural History. Arcadia Publishing. 2006.

  5. Raiche, R. California Buckeye: A Tree for All Seasons. Pacific Horticulture. Jan. 2009. http://www.pacifichorticulture.org/articles/california-buckeye-a-tree-for-all-seasons/ 

  6. California Buckeye. Aesculus californica. California Native Plant Society. http://calscape.org/Aesculus-californica-()

  7. Ridgeway, S. Aesculus californicus. California Buckeye. Univ. of California UC Master Gardener Program. http://sonomamg.ucanr.edu/Plant_of_the_Month/Aesculus_californica_-_California_buckeye/

  8. Rose, Evelyn. A-Foresting We Will Go. A History of Trees in San Francisco. Part I. Blog Post. August 2013. http://www.trampsofsanfrancisco.com/a-foresting-we-will-go-a-history-of-trees-in-san-francisco/

  9. Prunus Ilicifolia. Wikipedia. https://en.wikipedia.org/wiki/Prunus_ilicifolia

  10. Hollyleaf Cherry. Prunus Ilicifolia. California Native Plant Society. https://en.wikipedia.org/wiki/Prunus_ilicifolia

  11. Anderson, M. Kat. Tending the Wild. Native American Knowledge and the Management of California’s Natural Resources. Univ. of California Press. 2005

  12. Hollyleaf Cherry. Prunus Ilicifolia. USDA NRCS Plant Guide. https://plants.usda.gov/plantguide/pdf/cs_pril.pdf

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