2. Eichhornia azurea (Swartz) Kunth, Eichhornia. 4. 1842.
Pontederia azurea Swartz, Prodr., 57. 1788
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.