AgPest » Sedges

Cyperus brevifolius

Carex inversa (leaves 5-10 cm, flower stems 10-20 cm) very grass-like 1 mm wide leaves, upright flower stems with 3-5 closely spaced short spikes
Carex divulsa (leaves up to 20 cm, flower stems up to 60 cm) very grass-like 3 mm wide leaves, upright flower stems with 6-10 widely spaced short spikes
Cyperus brevifolius (up to 30 cm) grass-like, flat, 1-3 mm wide leaves. Compact flowerhead with 3 long leaf-like bracts below
Carex comans (6-25 cm) red, brown (occasionally green) drooping leaves forming an unpalatable tussock
Carex longebrachiata or Australian sedge (30-90 cm) found in dryland/hill country. Long drooping seed heads
Carex geminata or rautahi (up to 1.5 m) rhizomatous, unpalatable sedge of wet areas in pastures. Sharp edged, double folded (‘w’ shaped in section) leaves and large drooping seed heads
There are many other sedges, found along streams, ditches and in swamps, which are not described here. For a more complete treatment of sedges see ‘An Illustrated Guide to Common Grasses, Sedges and Rushes’.

Carex inversa, Carex comans and Carex geminata are natives. Carex divulsa, Carex longebrachiata and Cyperus brevifolius are all introduced species.

Most of these species can be found throughout New Zealand, although Australian sedge is more abundant in the drier parts of the North Island and upper South Island.

All these sedges are perennials with short, thick to widely spreading rhizomes. Some of the smaller sedges have an annual growth habit, with shoots dying back to underground rhizomes during winter, however, the larger sedges have leaves present throughout the year. All are prolific seed producers.

The combination of mat-forming rhizomes and prolific seeding can make these sedges highly invasive of poor or damp pastures
All these species can invade pastures to a greater or lesser extent depending on conditions
They are unpalatable to livestock and reduce pasture utilisation
Once established they are very difficult to eradicate.

Can invade croplands that are very wet in winter and persist through drier months
May clog drains, leading to increased water retention, and interfere with spring crop establishment.

Sedges are non-toxic but are generally avoided by livestock. Therefore, the plants are expected to have little impact, apart from outcompeting palatable plant species.

Grazing management is not an option as these sedges are generally tough and unpalatable
Improving drainage and strong pastures are the best management tools
Repeat mowing will reduce seed production and sometimes kill the plants
Cultivation followed by discing, to chop up the root masses, will provide some control.

Few herbicides are effective on sedges, they are mostly tolerant of glyphosate used alone
Glufosinate offers partial control, with better control of seedlings
Halosulfuron (Sempra) is registered for control of nutsedge but may also offer activity on other sedges
Glyphosate/saflufenacil mixtures are reported to be effective on some sedges
These plants, especially Cyperus, are often found colonising areas where herbicides are used to control other weeds.

Champion P, James T, Popay I, Ford K 2012. An illustrated guide to common grasses, sedges and rushes of New Zealand. New Zealand Plant Protection Society, Lincoln, New Zealand. 182 p.
Holden P 2021/2022. New Zealand Novachem agrichemical manual. Agrimedia Ltd, Christchurch, New Zealand. 864 p.