Leather Oak :

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 or small tree, with a dense canopy
- 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)

Wildlife
- 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
  - Larval food source (host) for the sleepy duskywing butterfly (Erynnis brizo)
- Pollen source for bees
  - Bees do not help pollinate oaks, which are wind-pollinated, because female oak flowers offer no nectar, so there is no incentive for bees to visit and thus transfer pollen
- 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)
  - Galls are abnormal, tumorlike growths induced by parasites (e.g. insects, mites, or bacteria)
  - Many species of gall (cynipid) wasps co-opt an oak’s DNA to create a unique home and food for their larvae
  - Watch this short video on the amazing worlds of oak galls (KQED 2014)
Native People
- 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 highly irregular cycles; see Oak family to learn more

Notes

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 male flowers, and each tree bears thousands of catkins in any given year (Pavlik 2014)
Edgewood’s leather oak is classified as a variety
- Q. durata var. durata is the most common variety of leather oak
- Variety indicates a population with small morphological variations, e.g. color, seen throughout the geographic range of the species; interbreeding is possible
- Subspecies indicates a geographically-separated population with distinct morphological characteristics; when not isolated, interbreeding is possible
- In practice, botanists have not consistently applied these ranks

ID Tips

See Oak family for comparative chart of oak lineages
May be confused with several evergreen trees/shrubs at Edgewood
- Coast live oak (Q. agrifolia var. agrifolia)
- Holly-leaved cherry (Prunus ilicifolia ssp. ilicifolia)
- Coast silk tassel (Garrya elliptica)

Underside of Leaf of Coast Live Oak (L), Leather Oak (LM), Holly-leaved Cherry (RM), Coast Silk Tassel (R) © DSchiel

	Coast Live Oak	Leather Oak	Holly-leaved Cherry	Coast Silk Tassel
Leaves
Shape	ovate	oblong to elliptic	widely ovate to round	elliptic
Margin	often wavy and curled ⋯ some spines	wavy and curled ⋯ many spines	wavy, but not curled ⋯ many spines	often wavy and curled ⋯ no spines
Upper Surface	matte 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 Surface	lighter green ⋯ possible hairy tufts at vein junctions	matte green ⋯ densely hairy	very shiny bright green ⋯ no hairs	gray-green ⋯ densely matted hairs
Flowers	male 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
Fruits	acorns	acorns	drupes	clustered 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

Specific References

KQED San Francisco. 2014, Nov. 18. What gall! The crazy cribs of parasitic wasps [Video]. Deep Look. YouTube.

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 J.E.D. Miller. 2020. An updated database of serpentine endemism in the California flora. Madroño 67(2): 85-104. BioOne Complete. PDF hosted by San Diego State University, San Diego, California.

Urban Forest Ecosystems Institute. A tree selection guide. California Polytechnic State University, San Luis Obispo, California.

U.S. Forest Service. Wind and water pollination. Forest Service. United States Department of Agriculture.

General References

Calflora Database. 2014. Berkeley, California.

Calscape. 2018. California Native Plant Society.

Charters, M.L. 2015. California Plant Names: Latin and Greek Meanings and Derivations.

Charters, M.L. 2017. Southern California Wildflowers: Guide to the Pronunciation of Specific, Generic and Family Names.

Corelli, T. 2004. Flowering Plants of Edgewood Natural Preserve (2nd. ed.). Monocot Press, Half Moon Bay, California.

Dave’s Garden.

Elpel, T.J. 2013. Botany in a Day: The Patterns Method of Plant Identification. HOPS Press, Pony, Montana.

Flora of North America. efloras.org.

Harris, J.G., and M.W. Harris. 2013. Plant Identification Terminology: An Illustrated Glossary. Spring Lake Publishing, Spring Lake, Utah.

Keator, G. 2009. California Plant Families. University of California Press, Berkeley and Los Angeles, California.

Native American Ethnobotany DB.

Regents of the University of California. Jepson eFlora. Jepson Herbarium. University of California, Berkeley.