Thread-leaved brodiaea is a purple-flowered perennial herb with flower stalks 8 to 16 inches tall. It blooms from late April to early June and is typically found on gentle hillsides, valleys, and floodplains within moderately moist plant communities having clay soils and varying amounts of sand and silt. This is a federally threatened plant occurring in portions of Los Angeles, San Bernardino, Riverside, Orange, and San Diego counties, California.