Limnophila R. Br.
ambulia, Asian marshweed
tropical Asia, Australasia, Africa
Limnophila aquatica Roxb.
L. aromatica (Lam.) Merr. (L. aromaticoides Yang & Yen)
L. australis Wannan & J.T. Waterh.
L. brownii Wannan
L. heterophylla (Roxb.) Benth.
L. indica (L.) Druce
L. rugosa (Roth) Merr.
L. sessiliflora (Vahl) Blume
U.S. Federal Noxious Weed: Limnophila sessiliflora
Identification: Limnophila sessiliflora is one of 13 aquatic to amphibious species of Limnophila, all of which are highly polymorphic in phenology. Consultation with published literature is recommended for accurate identification of this species. The small sessile flowers are somewhat typical of this species, but not reliable as a sole diagnostic feature.
L. sessiliflora (Vahl) Blume is an aquatic weed on the U.S. federal noxious weed list.
Annual or perennial, rooted. Stems ascending or creeping; adventitious roots produced from leaf nodes. Leaves highly variable in shape, caulescent, decussate or whorled, sessile or petiolate, distinctly heterophyllous between submersed and emersed forms; emersed leaf blade entire, ovate to lanceolate; submersed blades often highly pinnatisect; venation pinnate. Flowers solitary in leaf axils or in terminal or axillary spikes or leafy racemes, sessile or pedicellate; sepals 5, subequal; corolla tubular or funnel shaped, 2-lipped; adaxial lip entire or 2-lobed; abaxial lip 3-lobed; white, pink, purple or blue, sometimes with conspicuous spots. Dispersal by numerous seeds or by stem fragments.
rivers, lakes, and swamps
Limnophila contains 18 accepted species and several unresolved names, of which 13 are considered aquatic. Most species have an aromatic (‘turpentine’) odor when damaged. There is confusion concerning the identity of the species traded as L. aromatica and L. aromaticoides. Some authorities separate the two species based on the arrangement of submersed leaves (opposite or 3-whorled in L. aromatica; 3 to 10-whorled in L. aromaticoides). Recent consensus suggests that L. aromatica is simply a highly variable species in flower color and leaf arrangement, and L. aromaticoides is one such variety. Limnophila aromatica, also know as Rau om or Rau ngo (in Vietnamese), is sold widely as a fresh herb to garnish and flavor soups and curries. Limnophila aromatica is commonly confused with Penthorum sedoides (also known as wavy Limnophila). Species of Limnophila have highly variable leaf shape among species and between growth forms. Some species have a highly dissected submersed leaf shape, with simple emersed leaves; in other species both submersed and emersed leaves are simple with a slightly serrated margin. There are numerous Limnophila species in the trade where the species name is unknown.