Scotch Thistle Onopordum acanthium.
Origin. Eurasia.
Distribution in Canberra Region. Widespead in pastoral, riverine, and woodland areas.
CNP: dominant species in parts of Mt Ainslie, Mt Painter and Harcourt Hill.
Especially under trees and where livestock congregated.
CUP: less. Farmlands: variable levels of infestation.
Dispersal. Mainly local (windborn) and especially by livestock and kangaroos.
General description and biology
Biennial thistles with a relatively weak stem up to 2 m high, greenish white with broad spiny wings down the stems.
Flowers are purplish, appearing from December to February.
Seedlings appear usually in summer and autumn.
Rosettes: silvery-coloured leaves; appear early, often along with variegated rosettes.
Control methods
a. Manual methods
Can easily be pulled out or cut with loppers/secateurs; or brushcutter (if stems <1 cm).
They don�t tend to grow again.
Rosettes can be quite easily cut off just below ground level with a mattock or mini-pick; less easily, with loppers. Getting them at the rosette stage is really the best strategy.
Because biennial, roots may grow deeper, so deeper chipping with mattock is desirable.
b. Chemical methods
As for Variegated thistle. More difficult to control with herbicides.
Alternative: dab glyphosate on centre of rosette, using spraybottle or weed-brush.
Common Sowthistle (or Milk Thistle) Sonchus oleraceus.
Origin. Europe
Distribution in Canberra Region. Widespread in disturbed ares, especially roadsides and pasture areas and home gardens. Nowhere as dominant species.
Dispersal. Local, windborn or by rain or animals.
General description and biology
A common thistle in gardens, sometimes spreading (non-aggressively) to nature parks.
Can grow to 1.5 m high. Smooth- and weak stemmed.
Leaves rich green, multi-lobed, not spiny.
Flowers yellow, in irregular clusters arranged on tips of branches.
Control methods
a. Manual methods
This thistle can easily be controlled by pulling-out.
The stem is thickened near the base and should be held firmly so that the root comes out;
otherwise the stem breaks off. If this happens, the root should be dug out with a mattock.
Unlike other large thistles, cutting off the stem at any stage (even after flowering) is invariably followed by re-growth.
b. Chemical methods
Unlikely to be needed. Rosettes can be brushed with glyphosate using weed-brush.