Digitaria ischaemum
Smooth crab grass
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Family: Poaceae · Type: Grass · Not Native
Digitaria ischaemum (Smooth crab grass) is a non-native California grass in the Poaceae family, recognized by glabrous upper leaf surfaces and decumbent habit.
Smooth crab grass is a naturalized annual grass found in northern coastal, southern Sierra Nevada, Central Valley, central coastal, southern coastal, and desert regions in disturbed areas at elevations below 300 meters. Flowering from September to November, this plant produces purple spikelets less than 3 millimeters long arranged in multiple spreading branches. Growing with decumbent or ascending stems 15 to 50 centimeters tall that root at lower nodes, it spreads easily in disturbed ground. Its leaf blades are 1.5 to 12 centimeters long, 2.5 to 5 millimeters wide, with glabrous upper surfaces and smooth leaf sheaths. The plant's distinctive purple spikelets cluster along narrow-winged branch axes, making it easily recognizable in disturbed landscapes.
Identification and appearance
Key characters: 3 sympatric species; distinguished by glabrous upper leaf surfaces and decumbent habit
Habitat and range
Habitat: Disturbed areas
Elevation: < 300 m
California counties: Alameda, Butte, Humboldt, Los Angeles, Riverside, San Bernardino, San Francisco, Santa Clara, Santa Cruz, Ventura, Yolo, Orange, Marin, Sonoma, Sacramento, Napa, Santa Barbara, Siskiyou, Merced, Nevada, Madera, El Dorado, San Joaquin, Glenn, Plumas, Mariposa, Colusa, San Luis Obispo, Placer, Tehama, Tulare
Outside California: to eastern United States, native to Europe
Bloom period
Digitaria ischaemum blooms Sep-Nov.
How to tell it apart
vs Eleusine: Digitaria has flexible mature seeds; goosegrass has flattened hard seeds and often grows in a perfect rosette.; vs Cynodon: Digitaria has 3-10 finger-like branches; bermudagrass has 3-7 branches and spreads by aggressive stolons.; vs Ehrharta: Digitaria has finger-like branches with flexible seeds; veldtgrass has a pyramidal panicle with hardened lemmas.; vs Stenotaphrum: Digitaria has thin finger-like branches; St. Augustine grass has thick, flattened stems and embedded spikelets.; vs Cenchrus: Digitaria has open finger-like branches; sandbur has spikelets enclosed in spiny burs.
Frequently asked questions
Is Digitaria ischaemum native to California?
No. Digitaria ischaemum is not native to California (recorded as not native).
When does Digitaria ischaemum bloom?
Digitaria ischaemum blooms Sep-Nov.
Where in California does Digitaria ischaemum grow?
Digitaria ischaemum occurs in Alameda, Butte, Humboldt, Los Angeles, Riverside, San Bernardino, San Francisco, Santa Clara and other counties, at elevations of < 300 m.
What plant family does Digitaria ischaemum belong to?
Digitaria ischaemum is in the Poaceae family, genus Digitaria.
What habitat does Digitaria ischaemum grow in?
Digitaria ischaemum grows in Disturbed areas.
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.