Even in its native Argentina, where the relatively unpalatable serrated tussock and Chilean needle grass are used as fodder, lobed needle grass is regarded as a serious weed due to its invasiveness and competitiveness. It is drought tolerant and forms dense infestations.
Lobed needle grass is native to Uruguay, Argentina and southeastern Brazil. Its known distribution in Australia is limited to a few small infestations on the northern outskirts of Melbourne.
Lobed needle grass reproduces by seeds. Although the exact amount of seed produced is not known, both of the closely related species serrated tussock (N. trichotoma) and Chilean needle grass (N. neesiana) can produce tens of thousands of seeds per plant per year. The seeds are very sharp and clinging, and readily attach themselves to clothing, fur and equipment. Seeds can also be spread when soil is moved. Major roadworks near the site of one infestation led to the spread of lobed needle grass. Anecdotal evidence suggests that the seed is not carried by wind like serrated tussock.
Lobed needle grass is a type of spear grass. It is a perennial tussock-forming grass growing to about 1 m high. The leaves are narrow and rolled inwards and, like other tussock grasses, grow from the plant base.
The leaves possess a short (1 mm) transparent ‘ligule’, which is a small flap at the junction of the leaf blade and the leaf sheath. The ligule can be located by tracing a leaf down to where it joins the sheath and bending the leaf back at this point.
It has a single flower on each spikelet enclosed by two distinctive lobes. The body of the seed is 4–10 mm long and less than 1 mm wide. The bristle-like tail of the seed (the ‘awn’) is 45–85 mm long and well connected to the seed body at the ‘corona’, which is a long (up to 10 mm) white collar at the seed base.
Stipoid grasses (such as the Nassella species) generally invade sites that are already highly degraded with a history of disturbance, especially land with higher fertility soil that has been used for grazing or farming. Lobed needle grass has invaded open woodlands and native and introduced grasslands including grassland dominated by four other Nassella species. It grows mainly in open areas, in direct sunlight or light shade, on clay soils – its preferred soil type in South America. It is tolerant to waterlogging and appears to prefer wet depressions, but it also occurs on stony rises.
CRC for Australian Weed Management: David McLaren (DPI Vic/Weeds CRC), Linda Iaconis (DPI Vic), Neville Walsh (Vic Herbarium) and John Thorp (National Weeds Management Facilitator), David Cooke (APCC).
Because there are relatively few lobed needle grass infestations, and it can potentially be eradicated before it becomes established, any new outbreaks should be reported immediately to your local council weed officer. Do not try to control lobed needle grass without their expert assistance. Control effort that is poorly performed or not followed up can actually help spread the weed and worsen the problem.
Lobed needle grass (Nassella charruana) is not declared in NSW under the Noxious Weeds Act 1993.