Marsilea oligospora
Nelson's pepperwort
(c) Timothy McNitt, some rights reserved (CC BY) · licence
Family: Marsileaceae · Type: Herb · Native
Marsilea oligospora (Nelson's pepperwort) is a native California herb in the Marsileaceae family, recognized by key differences in leaflet symmetry and margin characteristics.
Nelson's pepperwort is a California native perennial found in the Klamath Ranges, northern California high-altitude regions, and Modoc Plateau in creek beds, flood basins, and vernal pools at elevations of 1,400 to 2,000 meters. This aquatic plant produces four-part leaves with hairy leaflets, each approximately symmetrical with straight or slightly concave sides and a truncate or convex distal margin. Growing with floating leaves having stalks around 15 centimeters long and other leaves with stalks 3 to 6 centimeters long, it spreads across wet seasonal habitats. Its leaflets are faintly fine-crenate, creating a delicate texture across the plant's surface. The sporangium cases are small, measuring 5 to 6 millimeters long and 3 to 4 millimeters wide, with unbranched stalks.
Identification and appearance
Key characters: 1 sympatric species; key differences in leaflet symmetry and margin characteristics
Habitat and range
Habitat: Creek beds, flood basins, vernal pools
Elevation: 1400-2000 m
California counties: Modoc, Sierra, Nevada, Trinity, Plumas, Butte, Shasta, Lassen, Tehama
Outside California: to Washington, Montana, Utah
How to tell it apart
vs Oxalis: Marsilea grows in water and has wedge-shaped leaflets; wood sorrel grows on land with heart-shaped or notched leaflets.; vs Trifolium: Marsilea is a fern with spore cases at leaf base; true clover is a legume with flowers and pods above ground.; vs Medicago: Marsilea has four equal leaflets; medick has three leaflets and produces coiled seed pods above ground.; vs Melilotus: Marsilea floats in water with four wedge-shaped leaflets; sweet clover is a tall land plant with narrow three-part leaves.; vs Hydrocotyle: Marsilea has four separate leaflets like a clover; pennywort has round, shield-like leaves attached at the center.
Frequently asked questions
Is Marsilea oligospora native to California?
Yes. Marsilea oligospora is native to California (recorded as native).
Where in California does Marsilea oligospora grow?
Marsilea oligospora occurs in Modoc, Sierra, Nevada, Trinity, Plumas, Butte, Shasta, Lassen and other counties, at elevations of 1400-2000 m.
What plant family does Marsilea oligospora belong to?
Marsilea oligospora is in the Marsileaceae family, genus Marsilea.
What habitat does Marsilea oligospora grow in?
Marsilea oligospora grows in Creek beds, flood basins, vernal pools.
Related species
Other California species in the same genus, family, or bioregion.
Sources: Jepson eFlora · Index of California Plant Names · CalPhotos
Last updated 2026-10-07
Data from The California Species Project — 14,000+ California species with verified data from CNPS, CDFW, USFWS, Cal-IPC, and more.