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Serrated tussock - Identification | LC0175 |
Keith Turnbull Research Institute, Frankston
October 2004 |  |
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This Landcare Note describes the weed serrated tussock, Nassella trichotoma.
See the Landcare Note LC0370 for information on serrated tussock management.
Common and scientific names
Serrated tussock
Nassella trichotoma (Nees) Hack. ex Archav.
Family Poaceae (grasses)
Figure 1. Serrated tussock leaves, flowering head, tussock.
Figure 2. Seed. Note long awn, attached off-centre to lemma, hairs on callus covering lower section of lemma, rough upper section of lemma.
Figure 3. Mature plant showing purplish seed heads drooping to touch the ground.
Figure 4. Seed heads in close up.
Figure 5. Infestation.
Description
Large, long-lived tussocks approximately 50 cm high, 15 to 25 cm diameter at base. Mature plants have drooping leaves that may extend plant diameter to 50 or 75 cm. Smaller plants on infertile soils (15 cm high).
Flowering stems - much-branched, initially erect, up to 95 cm long, twice as long as leaves. Droop at maturity to touch the ground. Shallot-like bases. Usually break off at base after seed set. Purplish soon after flowering, golden when seed is ripe.
Leaves - very numerous, thin, fine, 0.5 mm diameter, to 50 cm long, tightly rolled, appearing circular in cross-section, with small serrations, felt by running the leaf between the fingers from the tip to the base. Green in summer, yellow-green in winter, base white. Tips of old leaves bleached, fawn in colour. Distinctive ligule – rounded, white, membranous, hairless, 0.5 to 1 mm long, protrudes vertically at the junction of the leaf blade and the leaf sheath, continuous with sheath margins. Similar native grasses have smaller, differently shaped or hair-fringed ligules. Rolled between thumb and index finger, the leaves of native grasses feel as if they have flat edges (although they may be tightly inrolled). Those of serrated tussock roll smoothly, as if cylindrical.
Seeds - 1.5 to 2 mm long, pale brown to purplish at maturity, basal section with 1.2 mm long white silky hairs, upper section rough; awn 20 to 35 mm long, attached off-centre, twisted in lower one third and rough to touch. Enclosed by 2 purple or reddish-brown, 6 to 10 mm long bracts (glumes) tapering gradually to a point.
Roots - Diffuse, wiry, fibrous, mostly in top 20 cm of soil, some deeper.
Figure 6. Seed with glumes attached, and section of leaf blade and leaf sheath showing ligule (arrowed): a. serrated tussock; b. silver tussock, Poa labillardierei; c. spear grass, Austrostipa sp.; d. wallaby grass, Austrodanthonia sp.
The four other Nassella species naturalised in Victoria have seeds with a corona (a ring of hardened tissue at the apex of the lemma) like a raised crown or collar encircling the base of the awn.
Flowering period
Origin
Pampas of South America
Distribution
Figure 8. Sites where serrated tussock has been identfied.
Lifecycle
Seeds germinate mostly on bare ground after rain, with the largest germinations in spring. Germination occurs also in autumn and winter, and in response to soil disturbance, however seedlings can appear 2 to 4 weeks after significant rainfall at any time. If plants germinate in late summer and autumn and conditions are favourable they will produce seed in the following summer, but under some circumstances plants may not flower in the first year. Flowering may commence in early October but usually begins in early November. Ripe seed is produced about 8 weeks after the flowering panicles first emerge. Autumn flowering can occur if plants are prevented from flowering in spring. If not controlled, an area with scattered plants can become a moderately dense infestation after 5 years and a heavy infestation after a further 3 years. Laboratory-stored seed remains viable for 20 years, although viability of seed in a forest fell to 8% after 13 years.
Habitat and land use
A wide variety of climates with annual rainfalls of 450 to 1000 mm. Not limited by soil type or soil fertility. Favours well-drained areas. Tolerates freezing conditions. Pastures, roadsides, neglected areas, native grassland, grassy woodland, dry coastal vegetation.
Dispersal
Seeds prolifically, spreads rapidly, seed-heads carried along the ground by wind like tumbleweeds; also by moving water, on machinery and equipment and coats of livestock. Seed survives passage through the digestive tract of grazing animals, remains viable after 10 days in gut.
Acknowledgements
Compiled by Ian Faithfull. Fig. 1 Elizabeth Conabere; Fig. 2 Enid Mayfield; Fig. 3 Malcolm Campbell, NSW Agriculture; Fig. 7 John Weiss.f Victoria© State of Victoria, Department of Natural Resources and Environment 2002 Page 2
This publication may be of assistance to you but 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
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