|Common name:||soldier thistle|
|Scientific name:||Picnomon acarna (L.) Cass.|
|Other scientific name/s:|
|Other common name/s:|
Catchment management authority boundaries
Regionally prohibited in the North Central, Port Phillip and Western Port Catchments
Regionally controlled in the Goulburn Broken and North East Catchments
Restricted in the Mallee, Wimmera, Corangamite, Glenelg Hopkins, West Gippsland and East Gippsland Catchments
Herbaceous plant - Forb (flowering herbaceous plant - not a grass)
Soldier thistle is an erect annual herb growing to 1 m high. Yellow-green in appearance due to numerous yellow spines on the leaves.
Stems of soldier thistle are ranched with spiny wings and dense white hairs. They are woolly in appearance.
Soldier thistle leaves are covered with fine white hairs and yellow spines, 1-1.5 cm long. White hairs on the leaves give them a woolly appearance.Rosette leaves grow to 30 cm long while stem leaves alternate and are long and narrow, about 1-1.5 cm in length.
Soldier thistle has pink or purple flower heads, growing 2-4 cm long and can be solitary or in groups at the end of branches.Flowers are formed in late spring from September to November with the plant flowering in early summer.
The seeds of soldier thistle are smooth and shiny with a detachable parachute of bristles on one end about 4-6 mm long.Seed germinates mainly in autumn, but has been seen to germinate after sufficient summer rainfall in disturbed areas.
Growth and lifecycle
Method of reproduction and disperal
Wind is the main method of dispersal for this weed. Seeds can disperse over short distances and whole plants can also be blown around after breaking off at the base. Seeds can also be carried on animals, vehicles, machinery and in water.
Rate of growth and spread
Soldier thistle grows rapidly in spring, particularly on heavy red-brown soil and spreads fast in degraded areas with little competition. It can compete with crops in favourable conditions.
Seedbank propagule persistence
A small percentage of solder thistle seeds can remain viable in the soil for several years. Plants may appear on recently cultivated areas where there has been no seeding for several years.
Soldier thistle prefers semi-arid to sub humid areas of temperate regions on dry sandy or stony soils. It is a weed of roadsides, channel banks, neglected areas and occasionally cereal crops and pastures in areas with an annual rainfall of 300-600 mm.
In Victoria, soldier thistle is found in the Mallee and northern regions of the state.
The icons on the calendar below represent the times of year for flowering, seeding, germination, the dormancy period of Soldier thistle and also the optimum time for treatment.
Agricultural and economic impacts
Well established infestations of soldier thistle can compete with crops and choke harvesting equipment. The sharp spines of the plant can injure animals and are generally avoided by stock.
Prescribed measures for the control of noxious weeds
- Application of a registered herbicide
- Physical removal
Other management techniques
Changes in land use practices and spread prevention may also support soldier thistle management after implementing the prescribed measures above.
Parsons,W.T. and Cuthbertson, E.G. 2001, Noxious weeds of Australia, 2nd edn, Inkata Press,Melbourne & Sydney.
Department of Primary Industries, Soldier Thistle Regionally Prohibited Weed Fact Sheet, February 2010