Panicum rigidulum subsp. rigidulum
Redtop panicum, Redtop Panicum
Family: Poaceae · Type: Grass · Not Native
Panicum rigidulum subsp. rigidulum (Redtop panicum) is a non-native California grass in the Poaceae family, recognized by spikelets crowded on adaxial side of branches and folded leaf bases are distinctive.
Redtop panicum is a naturalized perennial grass found in the Sierra Nevada and Great Valley bioregions in ditches and riverbanks at elevations below 1,600 meters. Flowering from July to October, this grass produces small, pale green to brown spikelets clustered along branching inflorescences. Growing in dense clumps with stems 40 to 140 centimeters tall, it forms robust, upright bunches of vegetation. Its leaves are long and narrow, folding at the base, with blades 10 to 40 centimeters long and 2 to 12 millimeters wide, typically glabrous or sparsely hairy on the upper surface. The spikelets are small, approximately 1.6 to 2 millimeters long, with a distinctive tuft of minute hairs at the tip of the upper floret.
Identification and appearance
Key characters: 6 sympatric species; spikelets crowded on adaxial side of branches and folded leaf bases are distinctive
Habitat and range
Habitat: Ditches, riverbanks
Elevation: < 1600 m
Outside California: eastern and southeastern United States, Mexico
Bloom period
Panicum rigidulum subsp. rigidulum blooms Jul-Oct.
How to tell it apart
vs Deschampsia: Panicum has thick rigid lemmas and well-developed lower glumes; hairgrass has thin awned florets and tiny glumes.; vs Dichanthelium: Panicum has a single flowering period; rosette grass produces two distinct flower types (spring and summer).; vs Hilaria: Panicum has single spikelets on branches; curly mesquite has spikelets in clusters of three along a spike.; vs Sorghum: Panicum has single spikelets throughout panicle; sorghum has three-spikelet groups at branch tips.; vs Echinochloa: Panicum has a membranous ligule and panicle; barnyard grass lacks a ligule and has bristly branches.
Frequently asked questions
Is Panicum rigidulum subsp. rigidulum native to California?
No. Panicum rigidulum subsp. rigidulum is not native to California (recorded as not native).
When does Panicum rigidulum subsp. rigidulum bloom?
Panicum rigidulum subsp. rigidulum blooms Jul-Oct.
What plant family does Panicum rigidulum subsp. rigidulum belong to?
Panicum rigidulum subsp. rigidulum is in the Poaceae family, genus Panicum.
What habitat does Panicum rigidulum subsp. rigidulum grow in?
Panicum rigidulum subsp. rigidulum grows in Ditches, riverbanks.
Related species
Other California species in the same genus, family, or bioregion.
- Panicum sp. — Panic grass
- Panicum urvilleanum — Silky panic grass
- Panicum acuminatum — Western panicgrass
- Panicum acuminatum var. fasciculatum — Pacific panic grass
- Panicum acuminatum var. lindheimeri — Lindheimer panicgrass
- Panicum acuminatum var. thermale — Geysers panicum
- Parapholis incurva — Curved sicklegrass
- Parapholis sp. — Sickle grass
Sources: Jepson eFlora · 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.