Mossman river grass

Cenchrus echinatus
Grass
Alternate
Simple
No colour
Green

Mossman river grass or Mossman burr grass is an annual grass with prostate or erect stems forming loose tufts. Seedlings are erect, robust, hairless and have bright mid-green leaves. The leaf sheaths are purplish-red, especially in older seedlings. Mature plants form prostrate or ascending tufts with stout stems up to 90 cm, but mostly up to 60 cm. The leaves are flat and rather stiff, tapering towards the
tip. They are 5−25 cm long and 3−12 mm wide.

Common names 
Also known as: buffel grass, bur grass, burr grass, field sandbur, Galland's curse,, hedgehog grass,, innocent weed, Mossman burr grass, sandbur, seaforth burr, southern sandbur, southern sandbur grass,
Family 
Poaceae
Deciduous 
No
Flowering time 
Mostly during summer and autumn, will flower year round in moist tropical environment.
Native/Exotic 
Exotic
Origin 
This species is thought to be native to Central America and tropical North America, though it is now widespread throughout the tropical regions of the world
Notifiable 
No
State declaration 
Nil
Council declaration 
Class R – Reduce populations
Known distribution 

A very widespread species that is naturalised throughout the northern and central parts of Australia (i.e. throughout Queensland and the Northern Territory, in the south-western, western and northern parts of Western Australia, in some parts of northern and eastern New South Wales and in the north-western parts of South Australia). It is most common in the northern parts of Western Australia and in the coastal regions of Queensland.

Habitat 

It prefers sandy soils including at the beach, footpaths, roadsides, lawns, parks and disturbed areas. Mossman river grass is present in dryer inland areas of Australia.

Habit 

A mostly upright (i.e. erect or ascending) and loosely tufted short-lived (i.e. annual) grass, usually growing 25-60 cm tall, but occasionally reaching up to 1 m in height.

Impact and control methods 

Mossman River grass (Cenchrus echinatus) is mainly regarded as an environmental weed in northern Queensland, the Northern Territory, and the northern parts of Western Australia. This species was also recently listed as a priority environmental weed in at least one Natural Resource Management region. It is an aggressive competitor that colonises sandy soils, particularly along the coast, and can have a significant impact on coastal sand dune communities.
Though this species can provide good grazing when young, is becomes a pest in pastures if it is allowed to mature. The burrs also reduce the value of wool and make shearing hazardous. The spiny burrs also penetrate the hides of livestock causing injury and are also a problem in recreation areas. In addition, Mossman River grass (Cenchrus echinatus) is also an important weed of many summer crops in the tropical and sub-tropical regions of northern Australia.

Stem and leaves 

The stems (i.e. culms) are often branched and have hairless joints (i.e. glabrous nodes). Roots (i.e. adventitious roots) may occasionally be produced at the lowest stem joints (i.e. nodes).

The leaves consist of a sheath, which partially encloses the stem, and a spreading leaf blade. The leaf sheaths are usually hairless (i.e. glabrous), but occasionally have a few hairs, while the leaf blades usually have some hairs present, particularly along their margins. The leaf blades (5-25 cm long and 3-12 mm wide) are very elongated (i.e. linear) and gradually narrow to a pointed tip (i.e. acute apex). Where the leaf sheath meets the leaf blade there is a small structure (i.e. ligule) that consists of a tiny membrane (0.5-2 mm long) topped with a dense line of hairs (i.e. the ligule is a ciliated membrane). The leaf sheaths, especially those on younger plants, and lower stems often have a reddish or purplish-coloured tinge (particularly when growing in a sunny position).

Flowers and fruits 

The seed-head (i.e. inflorescence) is spike-like (i.e. spiciform), but is actually a reduced panicle (3-10 cm long and 1-1.3 cm wide). This seed-head consists of several to many (i.e. 5-50), stalkless (i.e. sessile) or almost stalkless (i.e. sub-sessile), burr-like structures (4-10 mm across), each bearing many sharp rigid spines (2-5 mm long) and also some hairy bristles or flexible spines. These 'burrs' contain a cluster of two to four flower spikelets, and each flower spikelet usually produces a single seed. The flower spikelets (4-7 mm long and 1-2 mm wide) are narrowly egg-shaped in outline (i.e. ovate) with pointed tips (i.e. acuminate apices). They consist of a pair of glumes (i.e. 1.3-5.7 mm long) and a pair of tiny flowers (i.e. florets). The lower floret is usually sterile or occasionally male, while the upper one has both male and female parts (i.e. it is bisexual). Each floret has two bracts (i.e. a palea and a lemma), the male ones have three stamens, and the bisexual ones also have an ovary topped with two feathery stigmas. Flowering occurs mostly during summer and autumn.

The 'burrs' are a reddish or purplish-green colour when young but turn straw-coloured or dark brown as they mature. They detach from the flowering stem entire, and may therefore contain more than one seed. The seeds (i.e. grains or caryopses) are broadly oval (i.e. elliptic) to egg-shaped (i.e. ovoid) and well hidden inside the burrs. These seeds (1.5-3.2 mm long and 1.3-2.2 mm wide) are brown and have a flattened tip (i.e. truncate apex).

Reproduction and dispersal 

This plant reproduces by seed, which are mostly spread when the spiny 'burrs' they are contained within become attached to animals, vehicles and clothing. These 'burrs' may also be dispersed by water and in contaminated agricultural produce (e.g. pasture seeds and wool).

Similar species 

Mossman River grass (Cenchrus echinatus) is very similar to the spiny burrgrasses (Cenchrus incertus and Cenchrus longispinus) and Birdwood grass (Cenchrus setigerus). These species can be distinguished by the following differences:

Mossman River grass (Cenchrus echinatus) has seed-heads that produce spiny 'burrs'. These 'burrs' are stalkless (i.e. sessile), have one row of larger flattened spines, and numerous smaller hairy bristles at their base. These spines are fused at the base (i.e. connate) and are joined together for some distance (2-5 mm).

spiny burrgrass (Cenchrus incertus) has seed-heads that produce spiny 'burrs'. These 'burrs' are almost stalkless (i.e. sub-sessile), have several rows of larger flattened spines (usually with only 8-25 spines in total), and numerous smaller hairy bristles at their base. These spines are fused at the base (i.e. connate) and are joined together for some distance (2-7 mm).

spiny burrgrass (Cenchrus longispinus) has seed-heads that produce spiny 'burrs'. These 'burrs' are shortly stalked (i.e. pedicellate), have several rows of larger flattened spines (usually with 40-70 spines in total), and numerous smaller hairy bristles at their base. These spines are fused at the base (i.e. connate) and are joined together for some distance (2-7 mm).

Birdwood grass (Cenchrus setigerus) has seed-heads that produce somewhat spiny 'burrs'. These 'burrs' have one row of larger flattened spiny bristles, and numerous smaller hairy bristles at their base. The flattened spiny bristles are fused at the base (i.e. connate) and are joined together for a short distance (1-3 mm).
It can also be confused with several other native and introduced species of grasses (i.e. Cenchrus spp. and Pennisetum spp.). To distinguish between all of these, a specialist text should therefore be consulted (e.g. Ausgrass: an interactive key to Australian grasses).