Saffron thistle

Did you know?
NutriLOGIC provides additional information on soil fertility and cotton nutrition through direct links to NUTRIpak and SOILpak

Home

Industry

Catchments

Communities

WEEDpak Section A1
Link enhanced for computer or tablet

Saffron thistle

Saffron Thistle Biology

Carthamus lanatus
Family: Asteraceae (Daisy family).

Common names: Saffron thistle, Distaff thistle, False star thistle, Woolly safflower, Woolly star thistle, Woolly thistle, Yellow star thistle.

Confused with: There are a number of thistles which may appear similar in the rosette stage. Saffron thistle is distinctive at the mature stage. Could be confused with safflower (C. tinctorius), star thistle (Centaurea calcitrapa), golden thistle (Scolymus hispanicus) and spotted golden thistle (S. maculates).

Description: Seedlings – the cotyledon leaves are glossy green and spoon shaped, 12 – 17 mm long by 6 – 9 mm wide.

Early leaves – the first true leaves spoon shaped, but with a more pointed tip. They are lightly serrated, with each serration tipped by a short spine, and have an indented, white central vein. Later leaves are more heavily serrated and become highly multi-lobed with each protrusion tipped by a sharp spine. Leaves grow up to 150 mm long. Plants form a dense rosette.

Later leaves – plants develop a central rigid, erect stem as temperatures rise in spring. Clasping, stalkless, rigid leaves develop along the stem. They are prominently veined, lobed and terminate with long, rigid, sharp spines. Numerous smaller spines tip the lobes along the sides of the leaves.

Plants - an erect annual herb, 80 - 120 cm tall with rigid stems. Plants are unbranched at the base, but become multi-branched towards the top. Each branch terminates with a flower head.

Flower heads – single heads develop at the end of each branch. The flowers are creamy yellow and are clasped within the flower head. The flowered head is surrounded by several rows of rigid, lobed leaves tipped and edged with spines. Head are 50 – 70 mm wide, including the spined leaves.

Seeds – are 5 – 7 mm long, grey-brown and wedge shaped. They are topped with a stiff pappus 7 – 10 mm long.

Lifecycle/Biology: An annual plant that germinates after rain in autumn or early winter and forms a dense, competitive rosette. In spring a rigid, erect central stem develops and the rosette leaves die off. Flowers develop in spring and early summer. Some plants may germinate following rain in spring and flower in late summer and autumn. Seeds of saffron thistle may remain dormant in the soil for several years.

Ecology: Adapted to a range of soil types, but most common on better soils with high fertility. Saffron thistle is a common invader of improved pastures and winter crops.

The problem: A competitive, widely occurring, major weed of winter crops, pastures and waste areas. Plants are palatable to livestock in the rosette stage, but are not eaten once the central stem develops. Spines can cause injuries and remain problematic for months after the plants mature. Mature plants can be a serious problem in cereal crops, choking harvesting equipment and contaminating grain samples. Seeds are difficult to remove by grading. Saffron thistle is readily controlled with herbicides such as 2,4-D amine in cereal crops, but is difficult to control in pastures where legumes are a valuable component of the pasture.

Distribution: One of the most widely distributed introduced weeds in Australia. Saffron thistle occurs in every state.

Origin: Originating from Europe.

References: Plants of Western New South Wales, p. 721 - 722.

Compiled by: Graham Charles

Print this page