Spirodela polyrrhiza
 
Larger Duckweed

Colony Bottom

Duck Mountain Provincial Park
25-July-2025

The distal portions of the roots have been removed from this specimen in order to clearly expose the undersides of the fronds. Note there is more than one root per frond.

The key answers below are from Rushes, Bulrushes & Pondweeds plus the remaining Monocots of Saskatchewan, Fascicle 6, Flora of Saskatchewan by V. L. Harms, A. L. Anna Leighton, and M. A. Vetter.

Spirodela: Answers to key questions leading to this genus 

Roots present, 1-21 per frond; fronds flat or gibbous, air spaces present and veins 1-21; daughter fronds and flowers arise in marginal pouches. NOT [Roots absent; fronds 3-dimensional (globular), without air spaces and without veins; daughter fronds arise from terminal pouches; flowers borne in dorsal cavities on upper frond surface.]

Roots more than 1 per frond; fronds purplish brown below, obovate to circular, up to 10 mm long; veins visible,  7 or more.  NOT [Roots 1 per frond; fronds green or reddish below, usually narrower but if obovate, then 4 mm long at most; veins difficult to distinguish, usually 3.]

 

Lemnaceae: Answers to key questions leading to this family. 

Plants free-floating aquatics growing on the surface or suspended in water, solitary and 0.5-15 mm across or attached together in larger colonies; identifiable stems and leaves absent. NOT [Plants larger and with well-defined stems and/or leaves]