old-world arrowhead

helium limnodium arrowhead thickets oldworld sagittaria sagittifolia river water macrophyte types leaves arrowshaped pink color flower northeast europe swamp potatoe delta duck wapato accretion silt aquatic plant vegetation backwash backwater bloom blossom bog botany braided environment estuary european fen flora fresh reservoir lentic marsh marshland mire slack slow current sludge setting wetland old-world water two arrow-shaped sticking flower