Blue vervain (Verbena hastata) in an open field at Geode State Park in Henry County, Iowa.

Details: 

Canon EOS 10D,  shutter 1/180second, aperture f11, ISO 400, Canon EF 100 mm macro lens.

Selected References:

Thieret John W, Niering William A, and Olmstead Nancy C. National Audubon Society Field Guide to North American Wildflowers, Eastern Region. New York: Alfred A. Knopf, Inc. Plate 591, P 816.

USDA-NRCS. "Plant profile for Verbena hastata."  The PLANTS Database (http://plants.usda.gov/ ). National Plant Data Center, Baton Rouge, LA 70874-4490 USA. 2004. < http://plants.usda.gov/cgi_bin/topics.cgi?earl=plant_profile.cgi&symbol=VEHA2   > (1 Aug. 2005).