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Name derivation:

“Many leaves” (Many Myrio- leaves –phyllum)


Whorled leaves (4-5) are pinnatifid, often described as similar to bird feathers.  Foliage submerged except on floral stems that differentiate from underwater sections by enlarging their girth to increase flotation, bend upward, and grow above the water surface by ~ 10 cm.  Aerial leaves are reduced in size and approach margins that are nearly ‘entire’ but with small ‘teeth’.  In northern ice-covered lakes most of the foliage ‘dies back’ leaving mainly the roots intact for growth after ice-out.

Roots are fibrous, extending 10 – 15 cm into organically-rich lake sediments.  Adventitious roots can form at nodes along the stem.  Asexual proliferation of plants can occur either from intact stems weighed down by epiphytes and acting as ‘runners’ along the sediment, or by fragmentation of the fragile stems followed by drifting and sinking.

Dwarf plants can be found growing in moist sandy substrates, with aerial leaves.  If subsequently submerged the plants develop leaves typical of their underwater foliage.

Because of morphological plasticity of leaves, flower presence is essential for identifying species.

Similar genera:

Because of its whorled leaves several other genera superficially are similar even though their leaf morphology differs significantly. These include submerged plants such as Elodea, Egeria and Hydrilla, as well as Ceratophyllum. All of these can form extensive 'canopies'.


Various species can grow in a variety of aquatic habitats from well-buffered calcium-rich waters to poorly buffered somewhat acidic lakes.  M. spicatum, considered invasive from South America into the USA, seems to prefer well-buffered waters. M. heterophyllum is considered native to Quebec and Ontario and NE US states (Godfrey and Wooten 1981), and proliferates in somewhat acidic lakes.  It is considered ‘naturalised’ in Europe.  The species is even considered to be ‘endangered’ in Ohio (online)



Godfrey, R.K., and J.W. Wooten  1981.  Aquatic and Wetland Plants of the Southeastern United States.  Dicotyledons.  University of Georgia Press. (712 pp.)