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Nodding Thistle

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Botanical Name: Carduus nutans
Other Common Names:

Declarations

 
Class Regions
Class 4Cabonne Council,Castlereagh Macquarie County Council,Cowra Council,Mid-Western Regional Council,Orange City Council,Upper Macquarie County Council,Wellington Council
Landholder Responsibilities: The growth and spread of the plant must be controlled according to the measures specified in a management plan published by the local control authority
Why Is It Bad?: Nodding thistle is a serious pasture weed in NSW tablelands. It has become an invasive, competitive weed in well drained annual pastures where sites have been disturbed at the end of summer. An erect annual or biennial herb growing to 1.6m high. The presence discourages animals from grazing neighbouring pasture plants, which reduces carrying capacity. The spiny heads contibute to vegetable fault in wool. The plants grow strongly throughout the autumn and winter months at a time when pasture production is at it's lowest. Dense patches also harbour pests such as rabbits.

Identification

Habit: Herb
Leaves: The leaves are light green in colour, they extend along the stems as wings, deeply dissected to the white midrib, they have irregularly toothed spiny lobes.
Flowers: The heads of the flowers are sessile or shortly pedunculate, globular with purple/mauve/pink/red or occasionally white florets surrounded by overlapping rows of spine tipped bracts. The flower heads droop or nod at right angles to the stem when mature.
Fruit: The seeds are grey to yellowish brown, 3 to 4mm long and slightly curved, shiny and marked with longitudinal lines and faint dots. Seed longevity in the paddock depends on depth of burial, those on or near the surface lose viability in 2 to 4 years, whereas seed buried may survive for at least 10 years.
Roots: A stout, branched and fleshy taproot to about 40cm deep.

Control Methods

Manual Removal: Removal by hand or cultivation is effective if the taproot is cut about 10cm below the soil surface and the soil removed from the roots.
Chemical Use: The plant is susceptible to MCPA and 2, 4-D if applied in spring when first buds appear.
Fire:
Slashing & Cutting: Mowing or slashing before the heads are developed prevents seed formation but does not kill the plant, because they can reshoot strongly from the buds near the base.
Biological Control: Overseas attempts have been made to control nodding with biological agents. In Europe the nodding thistle receptacle weevil, Rhinocyllus conicus, feeds on developing seeds in the thislte heads.
Grazing: Nodding thistle is not usually grazed due to the spiny foliage, although goats will graze the developing buds.
Cultivation & Scalping:
Smothering:
Solarisation:
Competition: The best way to control in most cases is to establish a perennial pasture which provides ground cover in late summer to compete with thistle seedlings.
Monitoring: After treating plants with chemical or manual removal, constant monitoring of the site is necessary for regrowth.
 




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