Potamogetonaceae . . . . . Pondweed family

This family includes two alternate-leaved genera: Potamogeton and Stuckenia, and the less common opposite-leaved genera: Groenlandia (Opposite-leaved pondweed - with lvs <9x as long as wide) and Zannichellia (Horned pondweeds - with lvs >10x as long as wide) (the latter not illustrated here)

At least 24 Br and Ire spp of Potamogetonaceae (plus some hybrids) have been recognised - they are often dificult to distinguish - so just a few typical images shown here; note esp. whether a sample has floating lvs or not

Potamogeton . . . . . Pondweeds

Potamogeton alpinus . . . . Red pondweed

Lakes, ponds etc., esp. on peaty soils, rare in S; tinged reddish, floating lvs translucent and mostly sessile

Potamogeton berchtoldii . . . . Small pondweed

The commonest submerged narrow-leaved sp.; arrows show stipules

Potamogeton crispus . . . . Curled pondweed

Lvs all submerged; Note minute teeth on leaf edges; frequent in ponds, streams etc. across BI

Potamogeton gramineus . . . . Various-leaved pondweed

Lakes, ponds etc., esp. on acid soils exc. S En; floating lvs opaque <9.5 x 3.4 cm; submerged lvs linear <14 x 1.2 cm

Potamogeton natans . . . . Broad-leaved pondweed

Common in ditches, ponds etc., esp. on rich soils; Floating lvs broad & opaque with discoloured flexible joint just below leaf blade; submerged lvs linear <4 mm wide

Potamogeton polygonifolius . . . Bog pondweed

Bogs and ponds on acid soil, exc. SE & C En

Stuckenia . . . . . Pondweeds

Previously included in Potamogeton

Stuckenia pectinatus . . . . Fennel pondweed

Fine leaves, totally submerged, even flowers; fruits v. asymmetric (pic 3); frequent in lakes, streams and ponds

The similar S. filiformis has much more symmetric fruits and rather local in Sc and NW Ire