Dirca
Dirca occidentalis
NATIVE – CA ENDEMIC
Description (Jepson, PlantID.net)
- Eudicotyledon
- Eudicots are a major lineage of flowering plants; see family for general characteristics
- Daphne Family (Thymelaeaceae)
- Winter deciduous shrub
- Grows from seed and rhizomes (horizontal underground stems)
- Leaves
- Alternate (1 leaf at each junction with stem) and simple (not divided into leaflets)
- Bright green and ovate-shaped, with silky hairs
- Appear in clusters concurrent with or after flowering
- Produced from the same bud as the flowers
- Flowers
- Inflorescence (flower arrangement) of 1-4 nodding flowers from the leaf axil (branching point)
- Open with or before the leaves
- Tiny scale-like petals
- Apparent petals are the bright yellow sepals (usually green, outer flower parts)
- Stamens (male flower parts) and pistil (female flower part) extend beyond the sepals
- Ovary superior (above the attachment of other flower parts)
- Inflorescence (flower arrangement) of 1-4 nodding flowers from the leaf axil (branching point)
- Fruit is a yellow-green, single-seeded berry (a usually multi-seeded fruit with a fleshy ovary wall), often mistaken for a drupe (a fleshy fruit with usually 1 seed in a hard inner shell — a stone fruit), infrequently produced
- Height to ~10 ft.
Distribution
- Native and endemic (limited) to the Bay area
- Grows in deciduous woodlands, chaparral, open scrublands, and broadleaf evergreen forests
- See Calflora for statewide observations of this plant
- California Rare Plant Rank: 1B.2 (rare, threatened, or endangered in California and elsewhere)
- Grows at elevations between 160 and 1,300 ft.
Uses (San Mateo County Parks prohibits removal of any natural material)
- Wildlife
- Anna’s hummingbird (Calypte anna) and non-native honey bees frequent the flowers (Graves 2008)
- Dusky-footed woodrats (Neotoma fuscipes) use the bark in the construction of their nests (Hudson 2021)
- Native people
- Fibrous bark of Dirca species was used for cordage and basketry because of its strong, tear-resistant, and pliable qualities (Klingaman 2011)
Name Derivation
- Dirca (DIR-kuh) – from a mythical fountain in Thebes, referring to the flower spray
- occidentalis (ok-sih-den-TAY-liss) – from the Latin for “the west”
- Leatherwood – refers to the plant’s pliable twigs and tough, leathery bark
Notes
- Flowers appear with emerging leaves
- First to appear will be a long pistil (female flower part) followed by many drooping stamens (male flower parts)
- Often found in California buckeye groves, which provide summer shade and winter sun
- Leatherwoods are relics from a cooler, wetter period during the Eocene, 55 to 34 million years ago (Klingaman 2011)
- Development of a Mediterranean climate and the tectonic activity that caused the formation of San Francisco Bay isolated its populations (Graves 2008)
- Populations are in decline over the last few decades due to habitat loss, slow rate of growth, limited seed dispersal, and poor seed germination
- Edgewood naturalist Ken Himes has speculated that leatherwood’s native pollinator may be extinct (Kiewall 2001)
ID Tips
- Check out this short video (Jepson 2020)
At Edgewood
- Found in moist woodlands
- Small, declining population along lower Sylvan trail
- A large population thrives on the slopes southeast of the Clarkia trail and smaller populations below the Edgewood and Sylvan trails
- See iNaturalist for observations of this plant
- Small, declining population along lower Sylvan trail
- Flowers January – March
Specific References
Charles, J. 2013, Feb. 5. Plant of the day: Western leatherwood. Flowers of Marin. Blog at WordPress.com.
Graves, W.R., and J.A. Schrader. 2008. At the interface of phylogenetics and population genetics, the phylogeography of Dirca occidentalis (Thymelaeaceae). American Journal of Botany 95: 1454-1465. Iowa State University Digital Repository.
Hudson, Z., and W. Graves. 2021, Nov. 23. Tensile strength of the bark of Dirca L. and other genera of Thymelaeaceae. Journal of the Torrey Botanical Society 149: 1-7. BioOne.
Jepson Herbarium. 2020, Apr. 9. Dirca occidentalis (Western leatherwood) [Video]. The Jepson Videos: Visual Guide to the Plants of California. The Regents of the University of California. YouTube.
Klingaman, G. 2011. Plant of the Week: Leatherwood. Cooperative Extension Service, Department of Agriculture, University of Arkansas.
Kriewall, J. 2001, May 29. Review of Three Dirca Species with Special Emphasis on D. Occidentalis. Jasper Ridge Biological Preserve, Docent Research Report. Stanford University.
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.
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.