Cyperus involucratus Rottb.
Rhizome short, stout. Stems to 60 cm high, stout, subterete. Leaves reduced to closely appressed, very pale brown basal sheaths. Involucral bracts many, ± equal, to 25 cm × 10 mm, > inflorescence, tips shortly acuminate. Inflorescence a compound umbel; rays many, to 8 cm long. Spikelets in small clusters at tips of rays, ± 4 × 2 mm, ovoid to linear-oblong, compressed, shining. Glumes densely imbricate, ± 2 mm long, ovate, obtuse, hyaline, white to light brown with green keel. Stamens 3. Style-branches 3. Nut ± ⅓ length of glume, trigonous, ovoid-ellipsoid, brown.
N. North Auckland - Rangaunu Harbour. S. Canterbury - Christchurch. (For many years the Rangaunu Harbour record was the only known occurrence as a garden escape; however, in recent years plants have escaped as seed from a Christchurch nursery.) (Africa)
First record: Healy and Edgar 1973: 25, as C. flabelliformis.
First collection: "Sandy place near Rangaunu Harbour, Mangonui Co.," H. B. Matthews, undated (CHR 5173).
Formerly known in N.Z. as C. flabelliformis Rottb. and C. alternifolius auct non L. Baijnath (Kew Bull. 30, 1975, 521-526) pointed out that the name C. involucratus predated C. flabelliformis and that C. alternifolius is a distinct sp. from Madagascar and Réunion Id.
C. involucratus is distinguished from other tall-growing spp. by the rigidly erect, obscurely 3-angled leafless stems with one to several light straw to purple-black sheaths.
C. involucratus is tolerant of cutting and resistant to herbicides. In horticulture it is generally known under the incorrect name - C. alternifolius and sometimes erroneously sold as "papyrus" The sp. is now increasingly planted about garden ponds and in pebble gardens in N.Z., and in Christchurch, has spread by seed from garden centres and domestic gardens and is proving a persistent weed, with Carex comans, in roadside gutter channels.
