West Highland Flora


Glyceria fluitans

Other name: Floating Sweet-grass

Glyceria fluitans

Photo Carl Farmer
8 Jun 2004 Isle of Rona, off Raasay

Frequent in marshy ground, ditches or shallow water

Stems to 1 m high, often much less.  Spikelets c 15-35 mm long, lemmas c 5.5-7 mm long.  Anthers c 1.5-3 mm long

ID: Glyceria species can be told by their long narrow spikelets, typically 10x as long as wide, with the whitish tips of the lemmas giving the alternating green and white effect as seen in the spikelet that nearly reaches the top left corner of the picture on the left.  The same pattern is seen in Poa and Festuca spikelets but they do not have such a high ratio of length to breadth.

The infloresence branches are mostly single or paired; when paired, the longer generally has 1-4 spikelets and the shorter 1 spikelet.  Many branches with 1 spikelet only will be found, especially near the top of the infloresence, usually with a stalk much shorter than the spikelet.

The species are difficult to tell apart. G declinata and G notata are like smaller versions of G fluitans.  Generally G fluitans has lemmas over 5.5 mm long, and the other 2 species have them under 5.5 mm.  These two species are supposed to have toothed lemma tips while G fluitans does not.  This is very difficult to see; essential to separate lemma from palea first, even then toothing or otherwise is difficult to distinguish from general tattiness, even on young lemmas.

The hybrid between G fluitans and G notata occurs in the area, and can be told by its infertility: the anthers don't open and the spikelets don't break up.

Other features: Leaves often float on water surface; in early spring a raft of floating leaves is often all that is visible of the plant.  Ligules 5-15 mm long, pointed.


Glyceria fluitans

Photo Carl Farmer
10 Jul 2004 Ord, Skye
Picture c 14.5 cm wide


Glyceria fluitans

Photo Carl Farmer
5 Sep 2004 Glenhinnisdale, Skye
New shoot c 20 cm from where exits water to central leaf tip

A "raft" of floating leaves with one emergent young shoot

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