Limnophila R. Br.
ambulia, Asian marshweed
tropical Asia, Australasia, Africa
Species commonly cultivated
Limnophila aquatica Roxb. (Asia)
L. aromatica (Lam.) Merr. (L. aromaticoides Yang & Yen) (Asia & Australia)
L. australis Wannan & J.T. Waterh. (Australia)
L. brownii Wannan (Australia)
L. heterophylla Benth. (Asia)
L. indica (L.) Druce (Asia & Australia)
L. sessiliflora (Vahl) Blume (Asia)
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.
Annual or perennial, rooted. Stems ascending or creeping; adventitious roots produced from leaf nodes. Leaves 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 36 species, 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.