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Scientific Name
Synonyms
Family
Common Names
Origin
Cultivation
Naturalised Distribution
Habitat
Habit
Distinguishing Features
Stems and Leaves
Flowers and Fruit
Reproduction and Dispersal
Environmental Impact
Legislation
Similar Species
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Click on images to enlarge

infestation along a waterway (Photo: Sheldon Navie)

habit (Photo: Sheldon Navie)

habit (Photo: Sheldon Navie)

reddish-brown leaf sheaths at the base of the stems (Photo: Sheldon Navie)

cluster of large leafy bracts at top of stem, prior to development of the seed-head (Photo: Sheldon Navie)

leafy bracts subtending a young seed-head (Photo: Sheldon Navie)

much-branched mature seed-head (Photo: Sheldon Navie)

close-up of mature seed-head showing clusters of spikelets at tips of branches (Photo: Sheldon Navie)

close-up of elongated flower spikelets (Photo: Sheldon Navie)

young plants (Photo: Sheldon Navie)

Cyperus involucratus

Scientific Name

Cyperus involucratus Rottb.

Synonyms

Cyperus alternifolius L. subsp. flabelliformis Kük.
Cyperus flabelliformis Rottb.

Family

Cyperaceae

Common Names

African sedge, dwarf papyrus grass, false papyrus, flat sedge, umbrella flatsedge, umbrella palm, umbrella plant, umbrella sedge, windmill sedge

Origin

Native to eastern Africa (i.e. Eritrea, Ethiopia, Somalia, Sudan, Kenya, Tanzania, Uganda, Malawi, Mozambique, Zimbabwe and South Africa), Madagascar and the Arabian Peninsula (i.e. Yemen).

Cultivation

Often cultivated as a garden ornamental, particularly in ponds and water features.

Naturalised Distribution

Widely naturalised in eastern Australia (i.e. in south-eastern, central and northern Queensland and in the coastal districts of central and northern New South Wales) and also scattered in the southern and northern parts of the country (i.e. in the coastal districts of Western Australia and in some parts of South Australia and the Northern Territory. Also naturalised on Lord Howe Island and Norfolk Island.

Widely naturalised elsewhere in tropical and sub-tropical regions of the world (e.g. southern USA, Hawaii, numerous Pacific islands and New Zealand).

Habitat

It is a weed of damp sites (e.g. creeks, wetlands, swamps, drainage channels and ditches) in tropical, sub-tropical and warmer temperate regions.

Habit

A long-lived (i.e. perennial) reed-like plant with upright (i.e. erect) stems usually growing 45-120 cm tall, but occasionally reaching up to 1.5 m in height.

Distinguishing Features

Stems and Leaves

The upright (i.e. erect) stems (3-5 mm thick) are rigid and triangular to almost cylindrical in cross-section (i.e. trigonous to sub-terete). They are hairless and sometimes slightly ridged lengthwise.

The true leaves are reduced to long sheaths that cover the bases of the stems. However, the very large leafy bracts that are clustered below the seed-heads (i.e. inflorescences) are often confused for leaves.

Flowers and Fruit

The seed-head (i.e. inflorescence) has about eight branches (5-10 cm long) which radiate outwards from the top of the stem. These branches are further divided into several some smaller branches (i.e. secondary branches) 1-2 cm long. At the base of the seed-head (i.e. inflorescence) is a cluster (i.e. whorl) of 12-22 large green leafy bracts. These bracts (up to 30 cm long and 2 cm wide) can easily be mistaken for leaves and are much longer than the branches of the seed-head. At the tips of the seed-head branches are the numerous elongated (i.e. oblong-lanceolate) and flattened flower spikelets that are arranged in dense clusters. These flower spikelets (3-9 mm long and 1.7-3 mm wide) are initially light green in colour, but they turn reddish-brown as they mature. Each flower spikelet consists of 6-30 tiny florets. The florets each have a bract (i.e. glume) about 2 mm long, a style topped with three elongated stigmas, and three stamens.

The 'seeds' (i.e. nuts or achenes) are yellowish or brown in colour, somewhat oval (i.e. ellipsoid) in shape, and three-sided or triangular in cross-section (i.e. trigonous). These seeds are about 1 mm long and have a projection at the tip (i.e. beaked apex) that is also about 1 mm long.

Reproduction and Dispersal

These species reproduces mainly by seed, though it can spread to form large clumps via short underground stems (i.e. rhizomes).

Seeds and stem segments (i.e. pieces of rhizome) are commonly dispersed to new areas by water and in dumped garden waste.

Environmental Impact

This species is regarded as an environmental weed in Queensland, Western Australia and the Northern Territory. It has escaped cultivation and become established along waterways and in wetlands, particularly near habitation. It is of particular concern in south-eastern Queensland, where it is very common along waterways and regarded to be among the top 100 most invasive plants. It has also been reported from conservation areas in South Australia (e.g. Cleland Conservation Park and Sturt Gorge Recreation Park).

Umbrella sedge (Cyperus involucratus) also invades marshy areas and stream edges in Hawaii, and in New Zealand it is a persistent weed of roadside gutter channels.

Legislation

Not declared or considered noxious by any state government authorities.

Similar Species

Umbrella sedge (Cyperus involucratus) is very similar to dwarf umbrella sedge (Cyperus albostriatus) and relatively similar to drain flat-sedge (Cyperus eragrostis), which is sometimes also called umbrella sedge. These species can be distinguished by the following differences: