Flower of puncturevine (Caltrop, Tribulus terrestris) in Washington-on-the-Brazos State Historic Site. Washington, Texas, August 29, 2010
Flower of puncturevine (Caltrop, Tribulus terrestris, Tribulus lanuginosus, local name hasak) on a roadside in southern Qatar, February 11, 2014
Puncturevine (Caltrop, Tribulus terrestris) with a yellow flower in Washington-on-the-Brazos State Historic Site. Washington, Texas, July 1, 2012
Small yellow flower of puncturevine (Caltrop, Tribulus terrestris) in Old Baylor Park. Independence, Texas, September 6, 2009
Yellow flowers of puncturevine (Caltrop, Tribulus terrestris, Tribulus lanuginosus, local name hasak) on a roadside in southern Qatar, February 11, 2014
Flower of puncturevine (Caltrop, Tribulus terrestris, Tribulus lanuginosus, local name hasak) in sand near a road to Saudi Arabia in southern Qatar, February 11, 2014
Caltrop flower (puncturevine, Tribulus terrestris) in Washington-on-the-Brazos State Historic Site. Washington, Texas, September 1, 2012