Nassella tenuissima and Nassella trichotoma
Poaceae (Gramineae) (grass) family
Also known as
finestem needlegrass, Stipa tenuissima (needlegrass) and Stipa trichotoma (nassella)
Where is it originally from?
Chile and Argentina
What does it look like?
Closely related to nassella tussock that has plagued farmers for decades, particularly in the South Island, finestem needlegrass has been mistakenly distributed as a native grass in several instances. It is a very fine grass with extremely tough, thin, round blades that don't break when pulled, and are rough to touch. Drooping flowering stems with open seedheads appear in spring, and the seeds give the plant a purplish-pink tinge when they ripen.
Are there any similar species?
Alternatives: There is a wide range of non-weedy ornamental native grasses now on the market, so ask at your local garden centre for ones that will grow well in your area.
Why is it weedy?
Finestem needlegrass forms dense colonies, producing masses of highly viable, well dispersed seed that last a long time in the soil and is spread on boots, clothing, wool, animal pelts and wind. Stock cannot digest this grass, and it forms balls in their stomachs, causing ill-thrift. It tolerates a wide range of climates and conditions, and is a particular threat to tall and short tussocklands in New Zealand, where it outcompetes native species.
How does it spread?
There is a wide range of non-weedy ornamental native grasses now on the market, so ask at your local garden centre for ones that will grow well in your area.
What damage does it do?
Form pure stands in low-growing plant communities, especially in harsh sites, and prevent the seedlings of native species establishing.
Which habitats is it likely to invade?
Disturbed shrubland, tall and short tussockland, bare land, river systems, rocky and coastal areas. Could potentially spread throughout New Zealand.
What can I do to get rid of it?
1. Grub (all year round): Remove soil from roots. Leave on site to rot down.
2. Spray dense spots amongst desirable broadleaved species (spring-summer): Gallant (5ml/L + crop oil).
3. Spray dense infestations only (all year round): glyphosate (15ml/L + penetrant).
What can I do to stop it coming back?
Cut rootstock and roots not completely grubbed from soil will resprout, and seed bank reinfests bared, burned or sprayed areas. Fire enhances seeding. Do not burn as fire enhances seedings, and exclude all livestock. Plant dense low cover where appropriate after control. Follow up on open sites for at least 10 years.