Themeda triandra

Themeda triandra is a tussock / clumping perennial grass, reaching a height of 1.5 metres with a spread of up to 1 metre. It is one of the foremost and well-known native grass species in Australia.

It has a very widespread and ubiquitous distribution across Australia, and also grows in Africa, Asia, New Zealand and other parts of the Pacific.

It grows in a wide range of habitats, including dry sclerophyll woodlands and forests as well as coastal shrublands and heathlands (on ocean cliffs) as well as inland arid shrublands. It can dominate some open paddock and grassy areas including road verges.

The family Poaceae is the grass family (any species outside this family should not be referred to as grasses). They are a group that a lot of us place in the “too-hard” basket but here are some simple facts about them: They are one of the largest groups of flowering plants, in the large monocotyledonous group (sedges, lillies, palms and orchids amongst others), with highly modified flowers and reduced perianth parts. Pollen from the anthers is generally wind-blown and is received by the female pistils. It is thought that grasses have evolved to dominate the planet over the last several 100,000 years, due to a general drying and cooling of many terrestrial areas. Hence, we have the grass-prairies of America, Africa and Australia, as well as other areas with a general reduction in vegetation like rainforests.

It is worth remembering that humanity relies heavily on the seeds of 3 grass species for food; namely Wheat (Triticum aestivum), Corn (Zea mays) and Rice (Oriza sativa) – not to mention fodder for agricultural meat.

Identification of grasses can be difficult if one is to plunge ‘in-depth’ but many genera can be identified by the appearance of their inflorescences. Different terminology is applied. Petals and sepals do not apply to flowers but rather structures such as glumes which are bracts that generally support the base of ‘spikelets’ (clusters of flowers or single flowers) with flowers generally called “florets”. Florets typically consist of a palea and a lemma (two joined structures which house the stamens and carpels). Florets can be bisexual or unisexual or sterile. In some genera, glumes are absent. Inflorescence structures are generally familiar, i.e. panicles, racemes, spikes etc).

There are a range of habits such as tussocks or clumping grasses (Poa, Themeda, Cymbopogon etc), to large clumping and running bamboos (world’s largest grasses) and stoloniferous grasses – those that creep prostrate over the ground using stolons (eg: turf grasses such as Kikuyu (*Cenchrus clandestinus) and Oplismenus aemulus).

Grasses produce simple leaves, usually made up of a blade and sheath with accompanying parts such as auricles, ligule and collars (where the blade joins the sheath).

In this species, leaves are 10-50 cm long and 2-5 mm wide, green to grey or blue, and ageing to an orange-brown in summer.

The stems with the flowering heads in grasses are called culms. In this species, they are to 1.5 metres tall.  The flowering period is from December to February. During this time plants produce large, distinctive, red-brown spikelets carried on branched stems. Spikelets have black awns (see image) that are retained by the seeds when shed. The spikelets make this perhaps the easiest of our native grasses to identify. This is true in our case as we find grasses, in general, particularly difficult to identify.

Grasses mainly produce a grain or caryopsis (there are some cases of berries, nuts and utricles). A grain is a fruit which is basically ‘all seed’ with very little associated tissue and can therefore germinate rapidly. In this species, they are about 1.5 cm long with a long thin awn to about 4 cm long.