Leather Oak

Leather Oak © DSchiel

Quercus durata var. durata
NATIVE – CA ENDEMIC

Description (Jepson, PlantID.net)

  • Eudicotyledon
    • Eudicots are a major lineage of flowering plants; see family for general characteristics
  • Oak Family (Fagaceae)
  • Small, drought-tolerant evergreen shrub to tree, largely confined to serpentine soils
  • Leaves
    • Small, tough, and densely organized
    • Curled under
    • Edges wavy and spine-tipped
    • Hairy, especially on lighter-green underside
  • Flowers
    • Separate male and female flowers on same plant (monoecious)
    • Male flowers on yellow-green catkins (long hanging clusters of small, petalless, unisexual flowers)
    • Female flowers are 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 up to 1 in. long
    • Variable in shape but often cylindrical
    • Warty, knobbed acorn cup
    • Matures in 1 year
  • Height to 10 ft.
  • Life-span is 50-150 years, much shorter than other oak species

Distribution

  • Native and endemic (limited) to California
    • Grows in chaparral and foothill woodlands usually in association with serpentine soil
    • 95% of plants occur on ultramafic soils, e.g.serpentine; see ultramafic affinity rankings (Calflora per Safford and Miller 2020)
      • Occasionally grows on other dry, rocky, nutrient-poor soils
    • See Calflora for statewide observations of this plant
  • Grows at elevations between 500 and 4,900 ft.
Male Flowers (L), Female Flowers (LM), Acorns (RM), Leaves (R)
© KKorbholz (L), DSchiel (LM, RM, R)

Uses (San Mateo County Parks prohibits removal of any natural material)

  • 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
      • Large mature trees, dead trees, and those with broken limbs are especially important for cavity-seeking mammals and birds
      • Several butterfly larvae use oaks as a host; leather oak is the specific host for the sleepy duskywing butterfly (Erynnis brizo)
  • 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

Name Derivation

  • Quercus (KWER-kus) – from the Latin for “oaks” from classical times; possibly from the Celtic quer, “fine,” and cuez, “tree”
  • durata (doo-RAY-tuh / doo-RAH-tuh) – from the Latin for “hardened,” “made callous,” or “hardy”
  • Leather oak – probably named for the tough, leathery leaves

Adaptations

  • Leaves are adapted for dry, hot chaparral
    • Small size means less evaporative surface area
    • High levels of lignin (structural component that stiffens plant tissue) reduce water loss, but are metabolically costly to maintain
    • Shape and dense hairs on underside maintain humidity for stomata (pores that allow gas exchanges)
  • Produces an especially abundant acorn crop (a mast) in irregular cycles, about every 5 years; see Oak family to learn more

Notes

Beaked Twig Gall
© KKorbholz
  • In the white oak evolutionary lineage (Section Quercus), commonly called the white 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)
  • Oaks, particularly those in the white oak lineage, host more gall insects than any other native tree or shrub in the western United States (Pavlik 2014 and Russo 2006)
    • 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
    • On leather oaks, look specifically for the beaked twig gall, induced by a cynipid wasp
  • Edgewood’s leather oak is classified as a variety
    • Q. durata var. durata is the most common 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

ID Tips

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

  • Found in serpentine chaparral
    • Look for leather oaks at the junction of the Sylvan and Serpentine trails as you come to the serpentine grasslands; many also grow along the upper Clarkia
    • A particularly large leather oak grows along the north side of the Sunset trail between posts 20-22
    • See iNaturalist for observations of Quercus durata
  • Flowers May – July

See General References

Specific References

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

Russo, R. 2006. Field Guide to Plant Galls of California and Other Western States. University of California Press, Berkeley and Los Angeles, California.

Safford, H.D. and Miller, J.E.D. 2020. An Updated Database of Serpentine Endemism in the California Flora. Madroño, 67(2), pp. 85-104.

Urban Forest Ecosystems Institute. A Tree Selection Guide. California Polytechnic State University, San Luis Obispo, California.

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