Damasonium alisma grows in acidic ponds. In
Great Britain it went into decline along with the village pond. It once grew in many English counties from
Sussex north to
Shropshire, but by 1900 was reduced to two ponds in
Buckinghamshire and one in
Surrey. It is gradually starting to make a comeback due to intense conservation efforts. It requires open, well-lit, shallow water to grow in and regularly churned-up mud for its seeds to germinate. It is very variable in form according to the depth of the water it is growing in. Dwarf plants with aerial leaves occur growing sub-terrestrially on mud. The number of ovules vary. Usually there are two in each carpel, but carpels with four to many occur over the range. Multi-ovulate forms from southwestern Europe and
Sicily were originally described as
D. polyspermum. The shape of the follicles depends on the number of seeds; the beak (empty upper part) of the carpel is elongated in two-seeded plants, whereas in many-seeded plants the seeds occupy more of the follicle and the beak is relatively shorter and less well defined. == Taxonomy ==