T.E.R:R.A.I.N - Taranaki Educational Resource: Research, Analysis and Information Network


Cyperus congestus (Purple umbrella sedge)

Kingdom: Plantae
(unranked): Angiosperms
(unranked): Monocots
(unranked): Commelinids
Order: Poales
Family: Cyperaceae
Genus: Cyperus
Species: C. congestus
Binominal name: Cyperus congestus
Synonym: Mariscus congestus
Common names: Purple umbrella sedge, Clustered flatsedge, Dense flat sedge.

Cyperus congestus is thickly, tufted, perennial sedge that is native to southern Africa (i.e. Lesotho, Namibia and South Africa) and is now a naturalised environmental weed in New Zealand. It is found throughout the North Island, Nelson, Marlborough and Canterbury. It is locally common in many areas. It is commonly a weed of roadsides, disturbed sites and it can be found in both damp and dry areas. It also invades wetlands and waterways.

Cyperus congestus grows up to 100 cm tall. Its stems are smooth and triangular and have swollen, pink/red bases.
The leaves (4-8 mm broad) are arranged in threes and they are shorter than stems. They are ridged with deep dip down the centre.
During summer to autumn the plant has single or a group of up to 7 red-purple round flower heads, each made up of 20 or so narrow flattened flower spikes. Each spikelet is >28mm long, smooth and are a red/brown colour. There are 3 to 6 long grass-like leaves immediately under each flower head at the end of flower stalk.
The plants fruit is a tiny nut which is triangular in cross section, narrow to pear-shaped and dark brown to black. The seeds are dispersed by contaminated machinery.

  

Flower heads photographed early March.   

Cyperus congestus seeds and spikelet