Phil Bendle Collection:Setaria palmifolia (Palmgrass)

Kingdom: Plantae
(unranked): Angiosperms
(unranked): Monocots
(unranked): Commelinids
Order: Poales
Family: Poaceae
Genus: Setaria
Species: S. palmifolia
Binomial name: Setaria palmifolia
Synonym: Panicum palmifolium
Common names: Palmgrass, Palm grass, Bristlegrass, Palm-leaf setaria grass, Pleated pigeon grass, Palmgrass, Highland pitpit, Hailans pitpit, Short pitpit, Broadleaved bristlegrass, Knotroot

Setaria palmifolia is a grass native to China, southern Japan, Taiwan, the Indian Sub-continent (i.e. India, Nepal, Pakistan and Sri Lanka) and south-eastern Asia (i.e. Myanmar, Thailand, Indonesia, Malaysia, Papua New Guinea and the Philippines).
It is the only grass with palm-like (plicate) leaves. It is known elsewhere as an introduced, and often invasive, species, including in Australia, New Zealand, many Pacific Islands, and the Americas. This invasive plant can disrupt native flora communities and ecosystems. In New Zealand, it invades disturbed and open forest, urban bushland, forest margins, watercourses (i.e. riparian areas), roadsides and waste areas. It prefers damp shady habitats. 
It spreads by its rhizomes and root masses resprouting constantly, thus forming tall monotypic stands. Setaria palmifolia forms a total groundcover with the shade of its wide leaves preventing the growth and establishment of seedlings of all other species. Birds are the common vector in seed dispersal. The spread of rhizomes and seeds are occasionally aided by water movement. Spreading also occurs in gardens and through dumped garden waste.

Setaria palmifolia is a perennial grass with stems growing up to two or three meters long from a knotty rhizome.
The stems can be up to a centimetre thick. It has bright green, hanging palm-like leaves (30-100 x 5-8 cm) with prominent veins running along their length. They taper to a point and are lightly covered in short strong hairs.
The narrow seed heads are on 1+ m long, greenish, cylindrical arching stems that stand above the leaves.
Its flower spikelets are arranged in large branched clusters (20-50 cm long)  that may be stiff or slightly drooping in nature. These flower spikelets (2-4 mm long) are usually subtended by a long bristle(4-10 mm long). Many small round seeds are produced.

This plant can easily be identified by the leaves that can be pulled apart like a concertina.

[1] 

A new shoot.

A developing seed head
[2]

A developing seedhead with spent heads behind.
[3]

The distinctive vertical concertina folds of the leaves [4]

The concertina-like surface of a leaf.
[5]

When a leaf dries the vertical concertina folds shrink.

The underside of the leaf.  
[6]

Seed head (July),[7]

A spent seedhead.
[8]

Seeds (July).
[9] 

A fertile floret.

Thanks to Wikipedia for text and information:https://creativecommons.org/licenses/by-sa/3.0/

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