pampas grass

Cortaderia selloana
Grass
Basal
Simple
White
Cream
Bluish-green
Discoloured

A very large, long-lived, tussock-forming grass with thick flowering stems growing 2-6 m tall. Its long and narrow leaves are very large (60-200 cm long and 3-20 mm across) and have very sharp, finely toothed margins. Their bases are pale yellow or whitish and as the leaves mature they droop down towards the ground. Its whitish seed-heads are large (25-100 cm long), plume-like and feathery in appearance (fading to light brown as they mature)separate male and female florets are usually produced on separate plants. Female florets have silky hairs (4-8 mm long) while male florets are hairless.

Common names 
Also known as: common pampas, common pampas grass, cut throat grass, pampas grass, silver pampas grass, silvergrass, Uruguayan pampas grass, white pampas grass,
Family 
Poaceae
Deciduous 
No
Flowering time 
Summer - Autumn
Native/Exotic 
Exotic
Origin 
Native to South America (i.e. Brazil, Argentina, Uruguay and Chile).
Notifiable 
No
Council declaration 
Class R – Reduce populations
Known distribution 

A widely distributed species that is naturalised mainly in the southern parts of Australia. It is most commonly found throughout Tasmania, in southern and central Victoria, in the ACT, in south-western Western Australia, and in the coastal and sub-coastal regions regions of central New South Wales. Also present in south-eastern South Australia and south-eastern Queensland and possibly naturalised on Norfolk Island. Infestations are common near the capital cities in most states (i.e. near Perth in Western Australia, Brisbane in Queensland, Sydney in New South Wales, Melbourne in Victoria and Adelaide in South Australia).

Habitat 

A weed of temperate, sub-tropical and occasionally semi-arid regions that prefers damp places, such as wetlands, swamps and stream banks. It also grows in disturbed sites, waste areas, bushland, open woodlands, grasslands, coastal environs, forestry plantations and along roadsides.

Habit 

A large, long-lived (i.e. perennial), tussock-forming grass with very large drooping leaves and flowering stems usually 2-4 m tall, but sometimes reaching up to 6 m in height.

Impact and control methods 

This species is regarded as an environmental weed in Victoria, New South Wales, ACT, Tasmania, Western Australia, South Australia and Queensland. It is actively managed by community groups in Tasmania, Western Australia, New South Wales and the ACT and is among the 200 most invasive plants in south-eastern Queensland. Pampas grass (Cortaderia selloana) prefers open sunny places that receive added moisture, and often invades damp places such as freshwater wetlands, stream banks and the margins of mangrove swamps. It has also spread into several drier plant communities including dry coastal forests, heathlands, open woodlands and grasslands. Infestations can become very dense, excluding most of the native ground flora and seriously impeding the recruitment of overstorey species. This species is also invasive in other parts of the world, and is listed in the Global Invasive Species Database.

Stem and leaves 

The relatively thick flowering stems (up to 3 cm across) are upright (i.e. erect) and grow 2-6 m tall. They are hollow and greyish-green to yellowish-green in colour. The large leaves consist of a short leaf sheath, that clasps the stem at the base, and a spreading leaf blade. Leaf sheaths may be smooth and hairless (i.e. glabrous) or somewhat hairy (i.e. pubescent) and their bases are a distinctive pale yellowish or whitish colour. The long and narrow (i.e. linear) leaf blades are very large (60-200 cm long and 3-20 mm wide), with pointed tips (i.e. acute apices) and very sharp, finely toothed (i.e. serrated) margins. They are slightly bluish-green (i.e. glaucous) above and generally dark green below, with a distinct midvein running lengthwise. A fringe of hairs (i.e. a ciliated ligule) 3-5 mm long is present where the leaf sheath meets the leaf blade. As the leaves mature they droop downwards, and they reach towards the ground in spirals once they are dead and dry.

Flowers and fruits 

The seed-head (25-100 cm long) is large, plume-like (i.e. an open panicle), feathery in appearance and initially white, cream or silvery (rarely pale pink or purple) in colour. These seed-heads are borne at the tips of the thick flowering stems (i.e. culms) and consist of large numbers of flower spikelets. Plants may have only female or male and female flowers (i.e. they are gynodioecious). Each of the flower spikelets (10-18 mm long) is narrow (i.e. lanceolate) and consists of a pair of bracts (i.e. glumes) and 2-7 florets (4-8 mm long). Female florets have silky hairs (4-8 mm long) while the male florets are hairless (i.e. glabrous). Flowering occurs mostly during late summer and autumn. The seed-heads fade to light brown or straw-coloured as they mature. Seeds (i.e. grains or caryopses) are narrowly oval (i.e. elliptic) in shape (2-3 mm long and about 0.6 mm wide), straw-coloured and enclosed within two 'bracts' (i.e. a palea and lemma).

Reproduction and dispersal 

This species reproduces mainly by seed, which can be produced in the normal way (i.e. by fertilisation) or vegetatively (i.e. by apomixis).Seeds are normally wind-dispersed, but may also be spread by water, machinery and in dumped garden waste.

Similar species 

Pampas grass (Cortaderia selloana) is very similar to pink pampas grass (Cortaderia jubata) and New Zealand pampas grass (Cortaderia richardii). These species can be distinguished by the following differences: pampas grass (Cortaderia selloana ) has relatively dense and very large seed-heads (25-100 cm long) that are usually whitish or silvery in colour when young. Its leaves are usually somewhat bluish-green or greyish-green (i.e. glaucous) in colour and have a very prominent midvein.pink pampas grass (Cortaderia jubata ) has relatively dense and very large seed-heads (30-90 cm long) that are usually pinkish or purplish in colour when young. Its leaves are usually bright green or dark green in colour and have a very prominent midvein.New Zealand pampas grass (Cortaderia richardii ) has relatively sparse seed-heads (30-60 cm long) that are usually whitish or pale brown in colour when young. Its leaves are usually somewhat bluish-green or greyish-green (i.e. glaucous) in colour, have a prominent midvein and also have distinct secondary veins. Pampas grass (Cortaderia selloana) is also relatively similar to giant reed (Arundo donax) and common reed (Phragmites australis). However, both of these species produce seed-heads at the top of stems that have numerous joints (i.e nodes) with alternately arranged leaves.