Flowers: July - October
Origin: Introduced from South America (although treated as native in CA by Jeps. Man.)
Conservation Status: Not of concern
PNW Herbaria: Specimen records of Xanthium spinosum in the Consortium of Pacific Northwest Herbaria database.
WA Flora Checklist: Xanthium spinosum checklist entry.
E-Flora BC: Xanthium spinosum atlas page.
CalPhotos: Xanthium spinosum photos.
USDA Plants: Xanthium spinosum information.