Sparganium Anna Leighton Key

This key was created by Anna Leighton (Harms, V.L., Leighton, A.L., Vetter M.A.  2018, Rushes, Bulrushes & Pondweeds plus the remaining Monocots  of Saskatchewan, published jointly by Flora of Saskatchewan Association and Nature Saskatchewan). 

1a. Stigmas usually 2, occasionally 1 on some flowers; mature fruit bodies 5-10 mm long, obpyramidal, abruptly contracted to beaks, sessile, usually 2-locular and 2-seeded; inflorescences usually branched; leaves emergent.  Sparganium eurycarpum  Giant Bur-Reed  C
1b. Stigmas 1; mature fruit bodies usually <5 mm long, ellipsoidal, fusiform or obovoid, tapering to beaks (+/- beakless in S. hyperboreum), stipitate or subsessile, 1-locular and 1-seeded; inflorescences branched or unbranched; leaves emergent or floating.  2

2a. Mature fruiting heads usually <10 mm wide; staminate heads single or apparently so; fruit bodies subsessile; inflorescences unbranched.  3
2b. Mature fruiting heads >10 mm wide; staminate heads usually 2 or more (1 in S. glomeratum); fruit bodies distinctly stipitate; inflorescences unbranched or branched.  4

3a. Lowermost pistillate heads axillary, usually sessile, sometimes pedunculate; mature fruit short beaked, the beaks 0.5-1.5 mm long; staminate heads remote from uppermost pistillate head; leaves 2-8 mm wide, thin, translucent, usually dark green.  Sparganium natans  Small Bur-Reed  C
3b. Lowermost pistillate heads supra-axillary; mature fruit essentially beakless, the beaks <0.5 mm long or absent; staminate heads contiguous or not with uppermost pistillate head; leaves 1-5 mm wide, rather thick, opaque, yellowish green.  Sparganium hyperboreum  Northern Bur-Reed  End (Lake Athabasca)

4a. Leaves (at least some) emergent, erect-ascending, keeled for all or part of their length; inflorescences unbranched.  5
4b. Leaves floating and flaccid, unkeeled; inflorescences unbranched or branched.  6

5a. Staminate heads 3-7 (10); pistillate heads contiguous or not distally; mature fruiting heads 15-35 mm wide; beaks 2-4.5 mm long.  Sparganium emersum  Green-Fruited Bur-Reed  C
5b. Staminate heads 1 (2); pistillate heads densely crowded distally; mature fruiting heads 12-16 (20) mm wide; beaks 1.5-2 mm long.  Sparganium glomeratum Clustered Bur-Reed  End (Churchill River)

6a. Inflorescences unbranched; leaves 2-5 (10) mm wide, flat to plano-convex; staminate heads (1) 2-4 per inflorescence, often contiguous and appearing as 1 elongate head; pistillate heads not contiguous; beaks of mature fruit 1.5-2 mm long, +/- straight; tepals not adnate to stipe.  Sparganium angustifolium  Narrow-Leaved Bur-Reed  C
6b. Inflorescences usually branched, sometimes unbranched; leaves 4-10 mm wide, flat; staminate heads 3-6 on the main rachis and 1-4 per branch of the inflorescence, contiguous or not; pistillate heads often contiguous or nearly so; beaks of mature fruit 2-3.5 mm long, curved; tepals adnate to stipe.  Sparganium fluctuans  Floating Bur-Reed  UC (boreal, north of Saskatchewan River)