Cyperus ustulatus aka Giant Umbrella Sedge

Cyperus ustulatus is a perennial in the sedge family, Cyperaceae. Kew lists its native range as New Zealand’s North Island and the Kermadec Islands. It places the plant in a subtropical climate. Plants For A Future also records it on the South and Chatham Islands. These records describe its habitat, rather than clearly defining its native range. It grows in lowland sites near rivers and on damp ground. Many of these sites lie near the coast.

The plant reaches about 4 feet [1.2 metres] in height. Kew describes its growth form as perennial or a rhizomatous geophyte. It has an extensive root system that helps bind sand. Its leaves provide material for woven goods and thatch. The supplied species evidence gives no leaf dimensions or colour. It also gives no detailed account of stems or fruit. The flowers have both male and female organs. No flowering season is given in the supplied records.

In gardens, this plant needs an open site without shade. It prefers moist or wet ground and suits a bog garden. A sandy loam is its preferred soil. It can also grow in light sandy or medium loamy soils. Its stated pH range spans mildly acid to mildly alkaline ground. Some forms may survive outdoors in Britain, according to Plants For A Future. This does not establish a hardiness rating for every form. The evidence gives no firm temperature limit.

Grow new plants from seed or divide established clumps. Sow seed on the surface in spring, keeping the compost moist. Germination takes two to six weeks at 18°C. Move seedlings into separate pots once large enough to handle. Keep them in a greenhouse through their first winter. Plant them outside in late spring after expected frosts. Divide clumps in spring or autumn. Large divisions can go straight into their final sites. Pot smaller pieces until they have rooted well. Autumn divisions benefit from winter shelter in a greenhouse.

Beyond bog gardens, the plant has practical uses. People use its leaves for hats, mats and roofing thatch. Its roots also help hold sand dunes in place. Plants For A Future lists no known edible or medicinal uses. It records no known hazards and does not flag weed potential. These statements do not prove that every use is safe. The supplied evidence names no pests or diseases.