Grass Identification: The Tribes of Grasses – 5 Brachypodieae

In Britain the tribe Brachypodieae has just a single genus: Brachypodium with two species. The tribe has affinities to Bromeae (hence the common name false-brome), and Triticeae and also Meliceae (a post on tribe Meliceae coming soon!).

The inflorescence is a raceme (an unbranched inflorescence with stalked spikelets).  The spikelets each have several-many florets which are all alike and cylindrical.  The glumes are persistent, unequal in length, and are 3-9 nerved.  The lemmas are 7-9 nerved with a straight awn at the apex.

The two species in Britain:

Brachypodium pinnatum (Tor-gass)

A strongly rhizomatous perennial, sheaths glabrous or shortly hairy, leaf blades erect and light or darker green, loosely hairy and 3.5-8.5 mm wide. Raceme erect 3-16 cm long,  with 5-14 spikelets, lanceolate to narrowly oblong, the lower 4.5-7 mm the upper 6-8.5 mm. Lemmas 8.5-11 mm often shortly hairy, with a terminal awn 1.5-4.5 mm. A grass of dry calcareous grassland in the south-east of Britain, forming extensive mono-dominant patches where grazing has been relaxed or abandoned.

The taxonomy of this species is currently under review, but this is beyond the scope of this post but check The Book of Stace page 1047 and Cope & Gray page 430-433 for more details.

Brachypodium sylvaticum (Wood False Brome)

Click on images to see more detail.

Brachypodium sylvaticum is atufted perennial, sheaths usually with spreading or reflexed hairs, leaves often bent over and characteristic bright green, blades flat and 4-12 mm wide and narrowed towards the sheath and loosely hairy.  Inflorescence a nodding raceme 6-12.5 cm long with 5-12 spikelets, lanceolate to narrowly oblong the lower 6-10 mm and the upper 8.5-15 mm, lemmas 9-13 mm shortly hairy, with a terminal awn 8-14 mm. Widespread and common grass of shady habitats such as woodland margins, rides hedgerows and roadsides and also calcareous grassland, limestone pavement and related habitats.

Next tribe is the lovely Meliceae!