1. UC IPM
Slenderflower thistle, <i>Carduus tenuiflorus,</i> has groups of 5 to 20 flower heads at the tops of stems, and its stem wings extend all the way to the flower heads.
Slenderflower thistle, Carduus tenuiflorus, has groups of 5 to 20 flower heads at the tops of stems, and its stem wings extend all the way to the flower heads.
Credit: Joseph M. DiTomaso