Euphorbia exstipulata var. exstipulata
Clark mountain spurge
(c) Elliott Gordon, some rights reserved (CC BY) · licence
Family: Euphorbiaceae · Type: Annual · Native
Conservation status: CNPS 2B.1
Euphorbia exstipulata var. exstipulata (Clark mountain spurge) is a native California annual in the Euphorbiaceae family, recognized by 4-ranked leaves and high elevation habitat diagnostic.
Clark mountain spurge is a rare (CNPS 2B.1) California native annual found in eastern desert mountains including the Clark and New York Mountains on rocky slopes at elevations of 1,800 to 2,000 meters. Flowering from September to October, this plant produces white petal-like appendages surrounding tiny cyathia with delicate involucral glands. Growing with erect stems less than 25 centimeters tall, the plant has spreading or ascending branches that are sparsely puberulent. Its opposite leaves are linear to lanceolate, 2 to 4 centimeters long, with slightly serrated edges and a symmetric base tapering to an acute tip. The fruit is a small spheric, lobed structure 2.5 to 3.4 millimeters long, bearing pyramidal seeds with distinctive transverse ridges.
Identification and appearance
Key characters: 13 sympatric species; 4-ranked leaves and high elevation habitat diagnostic
Habitat and range
Habitat: Rocky slopes
Elevation: 1800-2000 m
California counties: San Bernardino
Outside California: to Texas, Mexico. Other varieties in southwestern United States, Mexico
Bloom period
Euphorbia exstipulata var. exstipulata blooms Sep-Oct.
Conservation status
CNPS 2B.1
How to tell it apart
vs Croton: Euphorbia bleeds milky white latex and packs its flowers into a tiny cup (cyathium) rimmed with nectar glands; Croton has watery sap, stellate or scaly hairs, and ordinary small separate male and female flowers.; vs Stillingia: Euphorbia flowers sit in a gland-bearing cyathium; Stillingia bears its flowers in a spike with a pair of glands flanking each subtending bract and has no cyathium cup.; vs Ditaxis: Euphorbia has latex and the cyathium; Ditaxis has clear sap, 5-parted petaled male and female flowers, and 2-forked (malpighiaceous) hairs.; vs Asclepias: Both ooze milky sap, but Euphorbia's minute flowers cluster in a cyathium and ripen into a 3-lobed capsule; milkweeds have showy 5-parted flowers with a crown and paired follicles of plumed seeds.; vs Polygonum: Prostrate mat spurges leak milky sap when torn and have paired stipules with opposite leaves at the nodes; knotweeds have clear sap and a papery sheath (ocrea) wrapping each node.
Frequently asked questions
Is Euphorbia exstipulata var. exstipulata native to California?
Yes. Euphorbia exstipulata var. exstipulata is native to California (recorded as native).
When does Euphorbia exstipulata var. exstipulata bloom?
Euphorbia exstipulata var. exstipulata blooms Sep-Oct.
Where in California does Euphorbia exstipulata var. exstipulata grow?
Euphorbia exstipulata var. exstipulata occurs in San Bernardino, at elevations of 1800-2000 m.
What plant family does Euphorbia exstipulata var. exstipulata belong to?
Euphorbia exstipulata var. exstipulata is in the Euphorbiaceae family, genus Euphorbia.
Is Euphorbia exstipulata var. exstipulata rare or endangered?
Euphorbia exstipulata var. exstipulata carries California Rare Plant Rank 2B.1, state rank S2.
Related species
Other California species in the same genus, family, or bioregion.
Sources: Jepson eFlora · CNPS Rare Plant Inventory · Index of California Plant Names · CalPhotos · CDFW CNDDB
Last updated 2026-09-30
Data from The California Species Project — 14,000+ California species with verified data from CNPS, CDFW, USFWS, Cal-IPC, and more.