Plants perennial, typically rooted in mud. Vegetative stems elongate, developing to and growing at water surface. Flowering stems erect, 8-12 cm, glabrous, distal inter-node 2-10 cm. Sessile leaves submersed, alternate on elongate stem. Petiolate leaves emersed; stipule 7-13 cm, apex truncate; petiole never inflated, 11-25 cm; blade round, 7-16 × 2.3-16 cm. Spikes 7-50-flowered, individual flowers open 1 day only; spathes obovate, 3-6 cm; peduncle 1.9-15 cm, pubescent with orange hairs. Perianth blue or white, limb lobes obovate, 13-25 mm, margins erose, central distal lobe dark blue at base with yellow distal spot; proximal stamens 15-29 mm, distal 6-20 mm; anthers 1.2-2.3 mm; style 3-lobed. Seeds 10-13-winged, 1-1.8 × 0.8-1.1 mm.

Flowering (probably) Jun--Oct. Coastal rivers, lakes; 0--100 m; introduced; Fla.; Central America to South America (n Argentina).

Eichhornia azurea is on the USDA/APHIS noxious weeds list (D. C. Schmitz 1990) and is known only as a waif from several locations in Florida (R. G. Westbrooks 1990). It has been reported from Texas (L. H. Shinners 1962b), but this record was based on a misidentified specimen (Jones 1160, SMU) that actually is E. crassipes. All known populations in Florida have been eradicated by the Florida Department of Natural Resources. R. G. Westbrooks specifically noted a population growing in a residential estate pool in Palm Beach that was eradicated in June 1988. Another collection from Columbia County (N. Coile 5793, NBYC) was also eradicated.

The breeding system of Eichornia azurea, a tristylous species, is more like that of Pontederia species than that of E. crassipes (S. C. H. Barrett 1978). Populations typically have a mix of all three floral morphs, allowing for outcrossing.

The above description is based on South American material.