|
Chilean needle grass - identification | LC0256 |
Keith Turnbull Research Institute, Frankston
May, 1999 |  |
To view the Adobe Acrobat file, you will need the Adobe Acrobat reader. |  PDF 229 kb | |
This Landcare Note describes the weed Chilean needle grass, Nassella neesiana.
Common name
Chilean needle grass
Botanical name
Nassella neesiana (Trin. & Rupr.) Barkworth
Previously known as Stipa neesiana
Family Poaceae (Grasses)
Status
Chilean needle grass is not classed as noxious but is regarded as a serious emerging weed and an established community problem.
Origin and distribution
Probably introduced in the 1930s and 1940s from South America where it occurs in Argentina, Bolivia, Ecuador, Uruguay, southern Brazil and Chile. The earliest Victorian record is from Northcote in 1934. In Australia it occurs in temperate regions with annual rainfall of more than 500 mm, mainly in pastures and on roadsides and public land.
Figure 1. Distribution of Chilean needle grass.
Description
Chilean needle grass (Figure 3) is a tussocky perennial in the speargrass group of grasses growing to about 1 m high.
Leaves - hairless or sparsely hairy, flat or somewhat inrolled, to 30 cm long and 5 mm wide, with 3 mm long smooth ligules.
Flowers - the flowering head is a loose, sometimes interrupted panicle to 40 cm long (Figure 4).
Figure 2. Chilean needle grass infestation.
Figure 3. Chilean needle grass tussock.
Figure 4. Chilean needle grass in flower.
Seeds -these are the best feature to use in identification. Two types of seeds are produced by Chilean needle grass: normal seeds and stem seeds. Normal seeds (Figures 5 and 6) are produced at flowering. At the junction of the seed and the awn (tail of the seed) there is a raised crown (corona), a ridge of small teeth encircling the awn. The seeds of native Australian speargrasses (Austrostipa sp.) appear similar except they don’t have the corona (Figure 6). The seeds of Chilean needle grass are pale brown when mature, warty in texture, and hairless except along the midrib and near the callus (the base of the seed). They are mostly 8 to 10 mm long, with a 1 mm long corona and a 60 to 90 mm long awn which is twice bent, with 15 to 30 mm to the first bend. The awns do not readily detach from the seed and they often twist together at maturity. The seed is enclosed by two bracts (glumes) which are 16 to 25 mm long, purplish in colour and taper to a point (Figure 5).
Figure 5. Chilean needle grass seed with glumes still attached. Note the corona between the awn and the seed.
Figure 6. The normal seed of Chilean needle grass (top - note the corona) compared to a seed of a native spear grass, Austrostipa bigeniculata (bottom - note the absence of a corona),
The stem seeds are located at the nodes (swellings which give rise to leaves) of the flowering stem and are concealed by the leaf sheath which has been removed for the photo (Figure 7). These seeds allow the plant to reproduce even if flowering has been prevented.
Properties
Chilean needle grass is becoming a serious pasture and environmental weed in south-eastern Australia. It is very invasive and forms dense stands in pastures, bushland and roadsides. It tolerates drought and heavy grazing, giving it great potential to spread and over-run existing vegetation. The potential distribution of Chilean needle grass in Australia is estimated to exceed 40 million hectares.
Figure 7. Chilean needle grass has stem seeds (above) and normal seeds (below).
The presence of Chilean needle grass may reduce land value. During the warmer months large amounts of unpalatable flower stalks are produced, with very little leaf material, resulting in a severe reduction of summer stock carrying capacity. The vigour of Chilean needle grass can be partly explained by its efficient system of seed production. Up to 15,000 seeds per square meter can be found in the seed bank beneath infestations. These seeds remain viable for many years. The seeds have very sharp points that have been reported to penetrate and damage the fleece, skin and eyes of livestock.
Figure 8. Flowering period of Chilean needle grass.
Dispersal
The sharp-pointed seeds readily become attached to the coats of animals, clothing and machinery. Floodwaters play a significant role in seed dispersal.
Acknowledgements
Written by Mark Gardener. Photos by Chris Cooper and Mark Gardener. Edited by David McLaren and Ian Faithfull, May 1999.
This note replaces note number PP0086
The advice provided in this publication is intended as a source of information only. Always read the label before using any of the products mentioned. The State of Victoria and its employees do not guarantee that the publication is without flaw of any kind or is wholly appropriate for your particular purposes and therefore disclaims all liability for any error, loss or other consequence which may arise from you relying on any information in this publication.
|
