Cyperus congestus Vahl
Thickly tufted perennial. Stems 15-40- (80) cm high, rather robust, 3-angled, smooth, leafy and somewhat bulbous and woody at base. Leaves usually < stems, to 7 mm wide, flat, margins smooth below, scabrid towards tip; sheaths purple-brown, minute transverse septa evident. Involucral bracts 3-6, leaf-like, the lowest > inflorescence. Inflorescence a simple or compound umbel or reduced to a single head; rays 2-4, rather rigid, to 6 cm long. Spikelets numerous, 10-20 × 2 mm, narrow-linear, acute, in dense ovate or hemispherical reddish-purple spikes; rhachilla with membranous wings. Glumes ± 3 mm long, not closely imbricate, usually tightly appressed to rhachilla, oblong-elliptic, acute, many-nerved, keel green, margins deep red-purple. Stamens 3. Style-branches 3. Nut ± ½ length of glume, obovoid-oblong, trigonous, dark brown, apiculate.
N. North Auckland; Auckland; Gisborne - Opotiki, Tolaga Bay; Wellington - Waitotara. S. Nelson; Marlborough - Kaituna Valley; Canterbury - Christchurch. (S. Africa)
First record: Cheeseman 1906: 1089, as "Cyperus lucidus R. Br.". Allan (Handbk Nat. Fl. N.Z. 1940, 223) suggests that this is the "Cyperus sp." in Cheeseman' s list (T.N.Z.I. 15, 1883, 294) but there are no specimens of C. congestus among Cheeseman' s specimens from Mangonui at AK.
First collection: Maitai Valley, Nelson, Miss Harris, March 1891 (WELT 44280). A specimen (WELT 44282) collected by J. F. Armstrong from "Canterbury Plains between Timaru and Geraldine" is dated June 1878, but a note on the label states that Mr Armstrong was not certain of the exact locality of the collection.
Formerly known in N.Z. as C. lucidus auct. non R. Br. and Mariscus congestus (Vahl) C. B. Clarke.
C. congestus could be confused with C. eragrostis and large states of C. polystachyos, but is recognised by the usually swollen to ± bulbous stem bases, purple-brown sheaths, long, narrow spikelets and congested, reddish-purple inflorescences.
As it tolerates drier habitats than C. eragrostis, C. congestus is becoming a more prominent weed in waste places, and on margins of rivers, streams, swamps, and ditch banks. It seeds freely and is increasingly troublesome in domestic and market gardens, and intensively cultivated damp land. and has established along shingle verges of sealed roadways C. congestus is also occasional in bare or trampled sites in poor damp pastures, and does not appear to be palatable. In Christchurch gardens it is sometimes grown as an ornamental, has escaped and is locally persistent and a nuisance in roadside gutter channels.
In the Nelson district C. congestus has shown a marked increase in distribution and abundance during the past 20 years and continues to spread to new localities, in shingle from graders and motor vehicles. Its movement along the main Nelson-Blenheim highway illustrates this: from Wakapuaka it has moved progressively through the Whangamoa, and the Collins Valley and has recently established itself along road verges in the lower Kaituna Valley, Marlborough between Okaramio and Kaituna. It seems likely that this sp. will soon be spread by vehicles and graders out to the Wairau River and Wairau Plains and establish itself in habitats similar to those about Nelson.
