LARGE-FLOWERED WATERWEED

Egeria densa

Frogbit Family [Hydrocharitaceae]

month8aug month8sep month8sept

status
statusZneophyte
 
flower
flower8white
 
inner
inner8yellow
 
morph
morph8actino
 
petals
petalsZ3
 
stem
stem8round
 
sex
sexZdioecious
male only

August? Photo: © CRP
Flowers 1.2 to 2cm across flowering only occasionally, but also needs warm water to flower. It is dioecious, but only male plants occur in the UK (see below).


August? Photo: © CRP
The flowers are white with 3 petals and yellow parts in the centre.


August? Photo: © CRP
The leaves are in dense whorls of three, not as tightly curled as those of Curly Waterweed (Lagarosiphon major).


Easily confused with : other 'Waterweeds' belonging to differing genera.

It is not native to the UK (just to Brazil, Uruguay and Argentina) and occurs sporadically in the UK mainly in canals as throw-outs from garden ponds. It is a dioecious plant with male and female flowers on separate plants. But because only the male was imported, it does not spread by sexual means, but rather vegetatively. It is not as much a problem in the wild within the UK as many other 'waterweeds'. This is the only species of Egeria in the UK, but there exist 2 other species in the rest of the World. Other more vigorous 'Waterweeds' belong to differing genera: Elodea, Hydrilla and Lagarosiphon.

Large-flowered Waterweed does not flower often in the UK, and only when the water is warm. When growing, mainly in Central and Southern Britain and some canals and mill ponds in South Lancashire. Grows in shallow water from the bottom, and when it reaches the surface spreads horizontally into a thick floating raft blocking out the light to other species and aquatic life. It's only saving grace is that it is reported to produce some antibiotics which inhibit the growth of toxic blue-green algae.

The stems are up to 2m long whilst the leaves 10-30mm long, 1.5-4mm wide with an acute apex.


  Egeria densa  ⇐ Global Aspect ⇒ Hydrocharitaceae  

Distribution
 family8Frogbit family8Hydrocharitaceae

 BSBI maps
genus8Egeria
Egeria
(Large-Flowered Waterweed)

LARGE-FLOWERED WATERWEED

Egeria densa

Frogbit Family [Hydrocharitaceae]