Coast Live Oak

Coast Live Oak © DSchiel

Encina
Quercus agrifolia var. agrifolia
NATIVE

Description (Jepson, PlantID.net)

    • Eudicotyledon
      • Eudicots are a major lineage of flowering plants; see family for general characteristics
    • Oak Family (Fagaceae)
    • Evergreen tree
    • Bark of young trees is silvery gray and smooth, developing deep furrows and ridges with age
    • Leaves
      • Margins spine-tipped and often curled
      • Leaf shape and size varies, often on the same tree
    • Flowers
      • Separate male and female flowers on the same plant (monoecious)
      • Male flowers on yellow-green catkins (long hanging clusters of small, petalless, unisexual flowers)
      • Female flowers inconspicuous and often solitary, growing at leaf junctions of new branches
        • Ovary inferior (below the attachment of other flower parts)
    • Wind pollinated – see Oak family to learn more
    • Fruit is an acorn, which matures in 1 year
      • Acorns of other red oak species mature in 2 years
    • Height to 40 ft. with a diameter of 1 to 4 ft. and crowns to 130 ft. across
    • Average life span of 300 years
    Male Flowers (L), Female Flower (M), Acorns (R)
    © DSchiel (L,R), SBernhard (M)

    Distribution

      • Native to California
        • Grows in mixed-evergreen forest, oak woodlands, chaparral, coastal sagebrush, and valley grasslands
          • Only California native oak that thrives in the coastal environment; normally grows within 60 mi. of the Pacific Ocean
        • See Calflora for statewide observations of this plant
      • Outside California, grows into northern Baja California, Mexico
      • Grows at elevations to 4,700 ft.

      Uses (Picking or removing any natural material from public land is illegal)

        • Oaks are a keystone species, supporting a great number and variety of wildlife and other plants
          • Provide food (acorns, leaves, roots) and habitat for many mammals, birds, butterflies, amphibians, and insects
          • Especially important for cavity-seeking mammals and birds for food-storage, nesting, and protection
          • Larval food source for the California sister (Adelpha bredowii californica) and California hairstreak (Satyrium californicum) butterflies
          • Provide a substrate for lichens, mosses, and parasitic plants, like mistletoe
        • California oak moth larvae (Phryganidia californica) eat the leaves (Swain 2009)
          • In some years, moths can defoliated trees across entire woodlands
          • A healthy tree can survive extensive leaf loss
        • Oak acorns were an important food for Native people, who gathered them each fall, leached out the tannins, and ground them for making mush or bread
        • Because trunks are rarely straight and the wood warps on drying, coast live oak has little commercial value except as a fuel
          • The wood made a high-quality charcoal used, for example, in lime kilns and by blacksmiths where intense heat is required

        Name Derivation

          • Quercus (KWER-kus) – from the Latin for “oaks” from classical times; possibly from the Celtic quer,“fine,” and cuez, “tree”
          • agrifolia (ag-ri-FO-lee-a) – from the Latin agri,“field,” and folium, “leaf,” but many authorities believe the describing botanist or the printer made an error and that the name should have been aquifolia, “holly-leaved”…. (Charter 2015)
          • Coast live oak – “coast” as it is the only California oak adapted to thrive along the coasts; “live” refers to it being evergreen
          Young Tree with Protective Collar © SBernhard

          Adaptations

            • Tough evergreen leaves protect against water loss and allow a quick response to favorable conditions for year-long photosynthesis
              • Trade off – evergreen leaves are metabolically costly to build and maintain
            • Leaves often vary even on the same tree as the tree adapts to varying degrees of light
              • Outer canopy leaves tend to be smaller and thicker, with extra layers of photosynthetic cells to capture sunlight
              • Inner, shaded canopy leaves tend to be thinner, wider, and flatter, with only one layer of photosynthetic cells to capture the remaining filtered light
            • Have you noticed young coast live oaks that appear to have a collar at their base?
              • Young tree will respond to deer browsing by growing as a low, dense bush with small, very spiny leaves
              • When the tree is wide enough that deer can no longer reach the center, the trunk will shoot up and leaves will get larger and less spiny (Heiple 2020)
            • Produces an especially abundant acorn crop (a mast) in irregular cycles, about every 5 years; see Oak family to learn more
            • Acorn dispersal is adapted to maximize reproductive success (Steinberg 2002)
              • Most acorns drop in the fall, but, unlike those of other California oaks, some remain attached until spring, reducing loss to birds and small mammals
            Pumpkin Gall © DSchiel

            Notes

              • In the red oak evolutionary lineage (Section Lobatae), commonly called the red oak group; see Oak family to learn more about these lineages
              • Catkins have 25 to 100 individual flowers, and each tree bears thousands of catkins in any given year (Pavlik 2014)
              • Seed-caching animals aid in seed dispersal
                • Scrub-jays cache about 5,000 acorns each year, 800 acorns per acre
                • Although 95% of cached acorns will be eaten, the remaining acorns have a higher survival rate than uncached acorns because they’ve been carefully planted!
              • Extensive coast live oak woodlands around the Bay Area were cleared for agricultural and urban development
                • Crooked, gnarled growth habit and deep shade of mature coast live oaks created woodlands that seemed enchanted or haunted to early California visitors (Pavlik 2014)
              • Oaks host more gall insects than any other native tree or shrub in the western United States (Pavlik 2014)
                • Many species of insects can co-opt the oak’s DNA to create a unique home and food for their larvae in the form of a gall
              • Edgewood’s coast live oak is classified as a variety
                • Subspecies rank is used to recognize geographic distinctiveness, whereas variety rank is appropriate for variants seen throughout the geographic range of the species; in practice, these two ranks are not distinct
              • Susceptible to the fungus-like microorganism (Phytophthora ramorum) that causes Sudden Oak Death (SOD)
                • The other species at Edgewood known to be susceptible to SOD is Pacific madrone (Arbutus menziesii) when saplings
                • For a complete list of known hosts and host associates see USDA Risk Analysis for Phytophthora ramorum, pp.6-9

              ID Tips

                • See Oak family for comparative chart of oak lineages
                • Unlike other oaks, coast live oaks have tufts of brown hairs at the vein junctions (armpits) on the leaf undersurface
                • May be confused with several evergreen trees/shrubs at Edgewood
                Underside of Leaf of Coast Live Oak (L), Leather Oak (LM), Holly-leaved Cherry (RM), Coast Silk Tassel (R) © DSchiel
                Coast Live OakLeather OakHolly-leaved CherryCoast Silk Tassel
                Leaves
                   Shapeovateoblong to ellipticwidely ovate to roundelliptic
                   Marginoften wavy and curled

                some spines
                wavy and curled

                many spines
                wavy, but not curled

                many spines
                often wavy and curled

                no spines
                   Upper Surfacematte to shiny dark green

                no hairs
                matte to shiny dark green

                hairs when new
                very shiny bright green

                no hairs
                matte to shiny green

                no hairs
                   Lower Surfacelighter green

                possible hairy tufts at vein junctions
                matte green

                densely hairy
                very shiny bright green

                no hairs
                gray-green

                densely matted hairs
                Flowersmale catkins and small, solitary females

                on same plant
                male catkins and small, solitary females

                on same plant
                bisexual flowers

                in clusters
                male and female catkins

                on separate plants
                Fruitsacornsacornsdrupesclustered berries

                At Edgewood

                  • Dominant tree in most of Edgewood’s woodlands
                  • Flowers February – April

                  See General References

                  Specific References

                    Beidleman, L.H. and Kozloff, E.N. 2003. Plants of the San Francisco Bay Region: Mendocino to Monterey. University of California, Berkeley.

                      Heiple, P. 2020, May 22. Personal communication.

                        Pavlik, B., et al. 2014. Oaks of California. Cachuma Press, Los Olivos, California, and the California Oak Foundation.

                          Steinberg, P.D. 2002. Quercus agrifolia. Fire Effects Information System. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory.

                            Swain, S., et. al. 2009, Apr. Pest Notes: California Oakworm. Statewide Integrated Pest Management Program. University of California Agriculture and Natural Resources.

                              US Forest Service. Celebrating Flowers: Wind and Water Pollination. United States Department of Agriculture.