All these arrowhead flowers do look alike. Maybe the one basic difference is flower size? Grassleaf arrowhead has always seemed to have smaller flowers than many of the more robust species. Then I look it up, and there's maybe 2 mm difference. Turns out it's fuzzy filaments that set some of these less robust species apart in the identification key. So, next time I need to be a lot closer, and catch the fuzz. Grassleaf is of course aquatic, growing in shallow water or really muddy mud in AL, AR, AZ, CO, CT, DE, FL, GA, IA, IL, IN, KS, KY(T), LA, MA, MD, ME, MI, MN, MO, MS, NC, NH, NJ, NM, NY, OH(E), OK, PA, RI(S), SC, SD, TN(T), TX, VA, VT, WA, WI, WV, LB, NB, NF, NS, ON, PE, SK, and QC. Taylor Co FL, 7/8/18. Water-plantain family, Alismataceae.