Western Leatherwood :

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)
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), but is 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)
Native people
- Branches of other Dirca species were used by Native people on the East Coast for cordage and basketry (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 often appear before the leaves
- First to appear will be a long pistil (female flower part) followed by many drooping stamens (male flower parts)
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 from the Clarkia trail
- No iNaturalist observations are documented because locations of rare species are obscured
Flowers January – March

See General References

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.

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.