purpletop Rhodes grass

Chloris inflata
Grass
Basal
Simple
Purple
Green

A short-lived or long-lived tufted grass usually growing 20-100 cm tall. Its stems usually spread outwards at first with upright tips. Its long and narrow leaves (4-50 cm long and 2-10 mm wide) are mostly hairless. Its reddish-tinged or purplish seed -heads are borne at the tips of the stems. Each seed-head has several branches (4-8 cm long) that radiate from the same point. The branches have numerous flower spikelets, which leave two small bracts behind when they fall off.

Common names 
Also known as: airport grass, Mexican blue grass, purple top chloris, purple top Rhodes grass, purple-top chloris, purpletop chloris, purpletop Rhodes grass, swollen finger grass, swollen fingergrass, swollen windmill grass,
Family 
Poaceae
Deciduous 
No
Flowering time 
Summer
Native/Exotic 
Exotic
Origin 
This species is widespread in the tropics and sub-tropics, and its exact origin is uncertain. It is most likely native to Central and South America or perhaps south-eastern Asia.
Notifiable 
No
Council declaration 
SIL – Special Investigation List
Known distribution 

Widely naturalised in northern Australia (i.e. in northern, central and south-eastern Queensland, northern and north-western Western Australia, north-eastern South Australia and many parts of the Northern Territory).

Habitat 

A weed of roadsides, disturbed sites, waste areas, creek-banks (i.e. riparian vegetation), footpaths and gardens.

Habit 

A short-lived (i.e. annual) or long-lived (i.e. perennial) tufted grass usually growing 20-100 cm tall. Its flowering stems (i.e. culms) usually spread outwards at first with upright tips (i.e. they are decumbent or geniculately ascending).

Impact and control methods 

"Purpletop Rhodes grass (Chloris inflata) is an environmental weed in northern Australia (i.e. northern Queensland, the Northern Territory and northern Western Australia). In these regions it is an aggressive invader of degraded land and coastal sites, spreading from roadsides and pastures into natural habitats, where it out-competes native species.

This species is currently an emerging weed of roadsides, footpaths and disurbed sites in south-eastern Queensland. Once it becomes established in the region it may have the capability to spread from these sites into natural vegetation, like it has in northern Australia. Hence it should be regarded as a potential environmental weed in south-eastern Queensland."

Stem and leaves 

"The stems are hairless (i.e. glabrous) and usually somewhat flattened (i.e. compressed). Their joints (i.e. nodes) are swollen and often purplish in colour.

The leaves consist of a sheath, which partially encloses the stem, and a spreading leaf blade. They are mostly clustered at the base of the plant and also alternately arranged along the stems. The leaf blades (4-50 cm long and 2-10 mm wide) are very narrow (i.e. linear) with entire margins and narrow gradually to a point at the tip (i.e. attenuate apex). They are mostly hairless (i.e. glabrous), and where the leaf blade meets the leaf sheath there is a tiny membrane (0.3-0.6 mm long) topped with hairs (i.e. the ligule is a ciliate membrane)."

Flowers and fruits 

"The seed-heads (i.e. inflorescences) are borne at the top of the upright flowering stems (i.e. culms). They consist of several (5-20) branches (i.e. spikes) that radiate outwards from the same point (i.e. the inflorescence is digitate). The reddish-green to purplish flowering branches (4-8 cm long) are loosely arranged and sometimes droop downwards when young. Each flowering branch has numerous small flower spikelets arranged along it. These flower spikelets (2-2.5 mm long) consist of a pair of bracts (i.e. glumes) 1.2-2.5 mm long and three or four tiny flowers (i.e. florets). Many of the florets are barren, and only the lowest one in each spikelet normally produces a seed (i.e. the lowest is bisexual while the rest are sterile). The florets have two floral bracts (i.e. lemma and palea), three stamens and an ovary topped with a feathery two-branched stigma. Each flower spikelet is also topped with two tiny awns (4.5-7 mm long). Flowering occurs mostly during summer.

As the flower spikelets mature they turn dark brown or blackish and eventually fall off, leaving the pair of bracts (i.e. glumes) remaining on the seed-head branches. The seeds (i.e. grains or caryopses) are spindle-shaped (i.e. fusiform), but somewhat flattened (i.e. dorsally compressed), and 1.2-2 mm long. However, they remain hidden within the old flower parts (i.e. lemma and palea)."

Reproduction and dispersal 

This species reproduces mainly by seed, which may be spread by wind and water, and may also become attached to clothing, animals, vehicles and machinery. They may also be spread by slashers, graders, and in contaminated agricultural produce (e.g. pasture seed).

Similar species 

"Purpletop Rhodes grass (Chloris inflata) can be easily confused with Rhodes grass (Chloris gayana ) and feathertop Rhodes grass (Chloris virgata ). These species can be distinguished by the following differences:

■purpletop Rhodes grass (Chloris inflata) has seed-heads that are initially purplish in colour and spreading or drooping in nature. Its flower spikelets have three relatively small awns (all less than 7 mm long) and are hairy towards their tips.

■Rhodes grass (Chloris gayana ) has seed-heads that are initially greenish-brown in colour and spreading or drooping in nature. Its flower spikelets have one small and one very small awn (both usually less than 6 mm long) and are not very hairy.

■feathertop Rhodes grass (Chloris virgata ) has very feathery seed-heads that are initially greyish-green in colour and usually borne in a more upright position. Its flower spikelets of have two relatively large awns (5-15 mm long) and are hairy towards their tips.
It is also relatively similar to several native windmill grasses (Chloris spp.). However, these natives are usually shorter-lived (i.e. annuals), much smaller in stature (less than 70 cm tall), and always have less than ten seed-head branches."