Nymphaea dimorpha is a species of waterlily endemic to Madagascar.
This species exhibits two distinctive growth forms. The submerged growth form has very thin foliage with short petioles. The emergent form has floating leaves with longer petioles.
The chromosome count is n = 14. The genome size is 449.88 Mb.
Cleistogamy occurs in this species. It can produce flowers, which never open, but self-fertilise and never reach the water surface.
It grows in pools of water among slowly flowing streams. The pools, which are darkened with organic material, are shaded by the canopy of tropical forest.
This species was first described as Nymphaea minuta <small>K.C.Landon, R.A.Edwards & Nozaic</small> in 2006. Later, it was discovered that this was a Nomen illegitimum, as the name was preoccupied by the French fossil waterlily Nymphaea minuta <small>Saporta</small> described in 1891. Therefore, the new name Nymphaea dimorpha <small>I.M.Turner</small> was chosen in 2014.
The type specimen was collected in shaded rain pools beneath coastal forest near Tampolo, Madagascar in 1999.
It is a member of Nymphaea subgen. Brachyceras.
The specific epithet dimorpha references the two distinctive growth forms of this species. The prefix di- means "two", and -morph means shape.
It is easily cultivated and suitable for low-light conditions. In cultivation it may grow four times larger than plants observed in their natural habitat. This is due to better fertilisation. It is very sensitive to cold temperatures.
It is used in hybridisation to create new smaller waterlily cultivars.