Stems stout, very leafy; lvs all whorled, 2-5 cm, with 10-18 segments on each side, the lower segments much reduced, the rachis to 1 mm wide; petioles 5-7 mm; fls axillary to scarcely modified lvs in emergent infls; fr 1.5-2 mm, minutely granular; pls dioecious, only the pistillate, white fls known in N. Amer. Native of S. Amer., commonly cult. in aquaria and often escaped in s. U.S., n. to N.Y., W.Va., and Mo. (M. brasiliense)
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.
Godfrey and Wooten 1979, DiTomaso and Healy 2003, Correll and Johnston 1970, State of Washington Dept of Ecology
Duration: Perennial Nativity: Non-Native Lifeform: Forb/Herb General: Emergent aquatic perennial from stout rhizomes, often in colonies. Emergent portion of the stem up to 5 meters long, emersed (rising from the water) or trailing in the mud and erect to ascending. Stems gray-green to reddish, to 5 mm in diameter at base. Leaves: Whorled, 3-6 per node, stiff, usually with 20 or more linear-filiform divisions, appearing featherlike, grayish green, lobes alternate to opposite, to 7 mm long. Flowers: Minute and unisexual, usually solitary in the axils of unreduced leaves, 4 sepals and petals, sepals translucent white, to 1.5 mm long; female flowers sessile, about 1.5 mm long. Male flowers rarely seen. Fruits: Grooved or 4-ribbed, breaking apart into 4 one-seeded nutlets. Ecology: Found in sluggish waters, edges of streams, lakes, ponds, backwaters; flowers April-July. Distribution: Native to South America, now found in Africa and North America. US distribution is the south, southwest, and west coast. Notes: Tropical plant that becomes dormant to survive freezing conditions, often found growing in shallow water to 1.5 m deep. This plant has been noted at Chiricahua National Monument, but has not been formally documented there. It has a number of vouchers from lower desert, closer to Saguaro National Park. Probably escapes cultivation due to its common use in aquariums. Appears to reproduce from stem segments, as male plants are rarely seen, even in the native range. Ethnobotany: Unknown, but other species in the genus have uses. Etymology: Myriophyllum comes from Greek myrios for numberless, and phyllon for leaf, while aquaticum means found in the water. Synonyms: Enydria aquatica, Myriophyllum brasiliense, Myriophyllum proserpinacoides Editor: SBuckley,2010, AHazelton 2015