Sium suave Walter. Phen: Jun-Aug; Aug-Oct. Hab: Freshwater marshes, brackish marshes, swamp forests, in tidally or seasonally flooded hydrology. Dist: NL (Newfoundland) west to AK, south to Panhandle FL, n. peninsular FL, and CA; e. Russia, China, Korea, and Japan.
ID notes:The plant can be very coarse, up to 3 m in height and the stem to 5 cm in diameter. Submersed leaves are deeply dissected.
Origin/Endemic status: Native
Taxonomy Comments: The taxonomic status of Sium floridanum Small, known from se. VA south to GA, needs additional investigation; it is probably just a depauperate shade form.
Synonymy: = Ar, C, Fl7, FNA, GrPl, Il, K1, K3, K4, Mi, Mo2, NcTx, NE, NY, Pa, RAB, Tn, Tx, Va, W, WH3, WV; > Sium carsonii Durieu ex A.Gray; > Sium cicutaefolium Schrank – S; > Sium floridanum Small – F, G, GW2, MC, S; > Sium suave Walter – F, G, GW2, MC