Mexican waterlily or
Banana waterlily [Nymphaea mexicana Zucc.][NYMME][CDFA list:
B] Photographs Map
yellow waterlily, Castalia flava (Leit.) Greene
perennial with creeping stolons, floating leaves, and
showy yellow flowers. Plants can rapidly colonize shallow
waters. Heavy infestations in slow moving channels, lakes,
reservoirs, and ponds can restrict water movement, contribute
to siltation, increase evapotranspiration rates, and hinder recreation
activities. Introduced from Southeastern U.S. and Mexico as an
develop from stolons before seedlings mature.Early
leaves submerged. Cotyledons remain within seed coat. First leaf
linear. Subsequent leaves narrowly arrowhead-shaped, ~ 2-5 cm
long. First floating leaves resemble ~ 2-3 cm long mature leaves.
floating to emergent when crowded, nearly round, flat to cupped,
narrowly cleft at the base with edges often overlapping, 10-25
cm wide. Upper surfaces glabrous, glossy bright green, often brown
blotched. Lower surfaces often deep red to purplish-brown and
black-spotted. Leaves usually die during winter. New spring leaves
are submerged, narrowly arrowhead-shaped, ~ 2-7 cm long.
and UNDERGROUND STRUCTURES:Dormant in the cool season. Tubers vertical,
2-30 cm long, 1.5-6 cm in diameter, covered with long light-colored
hairs and persistent wart-like petiole bases, anchored by many
fibrous roots. Stolons creeping, white, ~ 1 cm in
diameter, grow from the upper portions of tubers. Stolon tips
have a few shoot buds and a cluster of banana-shaped storage
roots 2-3 cm long that overwinter buried in 20 cm or more of mud.
In spring, shoot buds elongate into stolons that produce new plants.
Tubers seldom survive drying conditions.
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Flowers musty-scented, bright yellow, 6-12 cm in diameter,
typically emergent to ~ 10 cm above the water surface.
Sepals 4, lanceolate to elliptic. Numerous petals
gradate into numerous smaller, petal-like stamens. Ovary
partially inferior, with curved finger-shaped stigmas.
Flowers open near noon and close late afternoon for 2 consecutive
days. Stigmas are receptive to insect pollination the first day.
Anthers shed pollen the second day. Closed flowers submerge to
and SEEDS:Berries submerged, green, ovoid, ~ 2.5 cm long,
burst to release 4-60 seeds with buoyant arils. Seed spherical,
~ 0.5 cm in diameter, dull greenish-black, covered with fine hairs.
CHARACTERISTICS:Mature leaves decay rapidly during the cool season.
HABITAT:Still or slow
moving shallow waters in lakes, ponds, streams, canals, and
Joaquin Valley. To 100 m (330 ft).
vegetatively from stolons and by
seed. New plants arise ~15-60 cm from the parent plant by
horizontal stolons. Seed disperses by floating. Seed does not
survive drying and must be submerged to germinate. Most germination
occurs at 19-23º C.
SIMILAR SPECIES:Fragrant waterlily [Nymphaea odorata
Aiton.][NYMOR] is also a noxious aquatic perennial of quiet shallow waters.
Unlike Mexican waterlily, fragrant waterlily has sweet-scented
white flowers and long, branched, creeping rhizomes 2-3
cm in diameter that are densely covered with short black hairs. Fragrant
waterlily grows in acidic to alkaline waters and has rhizomes that can tolerate
some desiccation. Seed germination in fragrant waterlily requires light and
the presence of ethylene, a gas whose production is stimulated when seeds are
crowded together. Germination is enhanced by cold stratification for several
months. This species is widely dispersed and expected to expand range. Sierra
Nevada, especially Lake Tahoe, Sacramento Valley (especially Butte Co.), San
Bernardino Mountains. To 2700 m (8850 ft). Introduced from the Eastern U.S.
Prevention and control: Yellow water lily was previously
introduced to California from Florida and Mexico for ornamental purposes. It
may infest lakes, ponds, or slow moving waterways and rapidly spreads in shallow
waters. Once established, yellow water lily is very difficult to eradicate.
Yellow water lily reproduces vegetatively by stolons and tubers which are difficult
to remove. Topgrowth can be cut and removed repeatedly to reduce populations.
However, regrowth will rapidly occur. Herbicide options include glyphosate and
fluridone. Consult the herbicide label for proper rate and timing. Treatment
of entire ponds should be done in sections to prevent low oxygen levels due
to decomposing plant material following herbicide application. There is little
information available for control of this species.
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