Arisaema :  key to North American Taxa
 
1a. Leaflets (3-5). Spadix blunt apically, shorter than
       spathe.                                                                    2. A. triphyllum
 
2b.  leaflets 5.                                                                 var. quinatum
 
2b.  leaflets 3.                                                                 3.
 
3a.  Leaves glaucous beneath at maturity. Spathe flange
       4.5 - 9.0 mm wide.  Spathe hood green or green with
       purple stripes. Sterile spadix appendage club-shaped,
      rarely cylindrical. Stomatal guard cell length mostly
      greater than 40 µm                                                   ssp. triphyllum
 
3b.  Leaves polished or lustrous beneath, not glaucous.
        Spathe flange 1-3 mm wide. Sterile spadix
         appendage cylindrical, rarely club-shaped. Stomatal
         guard cell length mostly less than 40 µm.           4.
                                                 
4a.  Spathe tube strongly fluted. Spathe hood green
       with white or purple stripes.                                ssp. stewardsonii
 
4b.  Spathe tube not fluted or rarely weakly fluted.
        Spathe hood green or purple, not striped.   ssp. pusillum
 
1b.  Leaflets (5-) 7-13 (-21). Spadix tapering apically,
        much longer than spathe.                                  4. A. dracontium
 
5a.  Spathe tightly inrolled around the spadix. To 1.5cm
       broad when unfurled.                                             var. dracontium
 
5b. Spathe flared distally, forming a blade, to 2.5cm
       broad.                                                              var. macrospathum
 
 
Based upon:
 
http://www.efloras.org/florataxon.aspx?flora_id=1&taxon_id=102590
 
Ward, Daniel B. (2012) Keys to the Flora of Florida – 31 Arisaema (Araceae).  Phytologia 94(2) pp. 151 – 158.