caltrop, Tribulus terrestris

Better to find caltrop before it finds you!  These pretty little flowers produce some of the fiercest burs on the planet.  They've been known to puncture tires - bicycles, not cars.  Imagine what they could do to your feet.  These plants form large mats, sprawling across dry open areas and waiting to hitch a ride.  They might come right through the soles of your shoes if they're worn a little thin.  This Mediterranean native is now found in AR, AZ, CA, CO, FL, HI, IA, ID, IL, IN, KS, KY, LA, MA, MD, MI, MN, MO, MS, MT, NC, ND, NE, NJ, NM, NV, NY, OH, OK, OR, PA, SC, SD, TN, TX, UT, VA, WA, WI, WY, BC, and ON.  Beal Gardens, MSU, 7/26/12.  Bean-caper family, Zygophyllaceae.