Weed of the month

The weed of the month is Chilean needle grass.

Nassella neesiana
Family Stipeae

• Chilean needle grass is an erect tussock grass that grows up to 1 m tall.
  The leaves are up to 5 mm wide with rough edges and they are ribbed on the upper surface.
• The distinctive, drooping flower heads are purple in colour, changing to pale brown when mature.
• Each seed is up to 10 mm long, with a hard, sharply-pointed head and a long, hair-like awn which is about 70 mm long.
• There are additional hidden seeds on the stem at the leaf nodes and at the base of the plant.

Where is it found?

Chilean needle grass comes from South America. It is typically found growing on dry grassland. It is currently known to occur in Auckland, Hawke's Bay and Marlborough, and was first found in North Canterbury in November 2008.

Why is it a problem?

Like the closely related nassella tussock (Nassella trichotoma), Chilean needle grass seeds prolifically and can displace pasture and native vegetation. It is relatively unpalatable to livestock when in seed, reducing the amount of stock able to graze during this period. It is spread by seeds attaching to clothing, equipment and the coats of animals. The sharp seeds are known to cause serious damage to livestock, will contaminate fleeces and can also downgrade carcasses.

Status

Chilean needle grass is an unwanted organism and is banned from sale, propagation and distribution throughout New Zealand.

Control

Prevention:
Put measures in place for your property to avoid spread via hay, stock, water, vehicles, machinery and soil movement from known contaminated districts. For small infestations, individual plants can be grubbed out and destroyed. Larger infestations should be treated annually with an appropriate herbicide before plants flower and set seed. Where necessary, treated areas should be revegetated with desirable pasture species. Chemical control is not always successful.