Thats really interesting about the vallis.and sea grasses. I wonder what the trigger for flowering is? I had always read / assumed that propagation was solely through runners. Does anyone else know of any other examples?
The adaptation of Ceratophyllum to a life under water is extreme. Its inconspicuous flowers open under water, and the pollen from the male flowers gets to the female flowers through the water (hydrophily).
I'm not sure exactly but Vallisneria spiralis would flower regularly in my low energy, which would suggest nothing very much in particular. Although I'm guessing daylight length and light intensity would be the usual triggers.