Form: herbaceous — perennial
Status: present in WA
Artichoke thistle is a native of the Mediterranean region. It was introduced to Australia late last century, either by accident with fodder or grain, or as an ornamental. It is common in Victoria and South Australia, and has occasionally been found in Western Australia.
It is found mainly on medium to heavy soils and generally in other areas such as roadsides, permanent pastures and waste land. Artichoke thistle is a potentially serious weed of pasture in higher rainfall areas of south-western Western Australia. When established, it dominates other plants by shading and by competing for moisture and nutrients. It can also compete with crops and impede harvesting.
Artichoke thistle is not poisonous, but the prickly nature of the plant deters sheep and cattle from grazing a heavy infestation. However, hungry stock will eat artichoke thistle foliage and survive on it, but it has a low nutritive value and may cause stomach impaction and mechanical injuries.
Leaves: Artichoke thistle forms a rosette of very large leaves up to one metre or more in diameter. The leaves are silky greyish-green on upper surface while the under surface appears almost white, because of the dense mat of white hairs. They are deeply divided, each lobe ending in a strong yellow spine. The first set of rosette leaves normally dies off over the summer and new leaves are formed in the following autumn.
Flowers: In spring a tall, branched flowering stem up to two metres high is produced. One large blue or purple flower forms at the end of each branch. The flower heads consist of tubular florets. They are surrounded by a series of rigid spines. Each plant may produce up to 50 heads. The plant occasionally flowers in the first year, but usually not until the second summer.
Seeds: The seeds are brown to black, about five millimetres long with a smooth covering. They are equipped with a "parachute" of feathery bristles about four centimetres long. Seeds are set in summer, germinate in autumn and rapidly form a large flat rosette of leaves and a deep tap root.
Agricultural and economic impact
Weed of pastures, spiny, low nutritional value.
Declared pest category
The Western Australian Organism List (WAOL) contains information on the area(s) in which this pest is declared and the control and keeping categories to which it has been assigned in Western Australia (WA). Use the links on this page to reach artichoke thistle in WAOL.
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When using any agricultural chemicals please ensure that you always follow instructions on the label and any permit. Users of agricultural chemical products must always strictly comply with the directions on the label and the conditions of any permit.
Only registered products can be used for weed and pest control.
Control methods for this plant can be found through the APVMA website, use "artichoke thistle" as the pest name.