Habit of saffron thistle

Early stages of flower development and leaves

Flower exhibiting the many yellow or cream florets

Flower surrounded by stiff, spiny, leaf like, hairy bracts

Scientific Name

Carthamus lanatus L.

Common Names

saffron thistle, distaff thistle, false star thistle, woldissel (South Africa), woolly safflower (Europe), woolly star thistle

Family

Asteraceae

Origin

Native to the Mediterranean region and Western Asia, it has spread to many temperate areas of the world, including the United States of America, Argentina, Chile, New Zealand and Australia. In Australia introduction of the plant was probably intentional, as it can be confused with a closely related safflower, and imported as a source of dye.

Habit

An erect, slightly hairy or sometimes woolly annual herb, growing about 1m or so tall, but more commonly standing 40-90cm tall. Reproduction is by seeds. The plant itself is rarely eaten but the seeds, which have a high oil and protein content, are eaten by sheep and birds. Saffron thistle generally dies during late autumn to early winter, and dead plants may remain standing for many months.

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Habitat

Saffron thistle is one of the most widely distributed introduced weed species in Australia. It is spread throughout most habitats and states, commonly dominating pastures and rangelands, of warm temperate and subtropical semi arid regions. It is most common in neglected pastures, roadsides and waste areas, particularly in low soil fertility and areas receiving 300 to 600mm of annual rainfall. Saffron thistle is an important weed of most cultivated crops and a contaminant of hay and grain. It is seldom found in better rainfall areas, given that pasture competition restricts its development.

 

General Description

Stems and Leaves:

The stems are white-yellowish white, but may be pale green in colour. They are rigid and ribbed with no wings and usually have minute hairs. Often it has a single stem with many branches on the upper part. The rosette leaves (a cluster of leaves at the base of a plant often lying flat against the ground) are up to 20cm long. They are deeply divided with broad terminal lobes, each lobe ending in a spine. Stem leaves are alternate, shorter, reflexed (turned abruptly backwards or downwards) and very rigid. They are prominently veined, lobed and spiny and are stem clasping; usually without hairs or sparsely downy on the upper surface.

Flowers and Fruit:

The flowering heads are made up of many yellow or cream florets (an individual flower usually small, forming part of a group of flowers arising from one stem) with faint red or black veins. The flowerheads are solitary at the end of branches. The florets are surrounded by stiff, spiny, leaf-like, hairy bracts (a small leaf-like appendage or scale which is immediately below a flower or infloresence) that are 3-5cm long. The fruit are large, grey-brown coloured cypselas (an inferior nut). The fruit is 4 sided, smooth and 5-8mm long. The fruit has a pappus (the appendages, hair or scales at the top of the seed) of several rows of stiff bristles or scales varying in length on one side of the seed. 

 

Distinguishing characteristics

The stems are rigid erect, branching near the top and ribbed with minute hairs. The leaves are stem clasping and lobed with each lobe ending in a spine. The infloresence is terminal with solitary heads with yellow tubular florets. The cypselas are large, being up to 6mm long with 6-8 tufts of bristles on one end.

 

Sources & References

Auld BA, Meld RW (1992) 'Weeds an illustrated botanical guide to the weeds of Australia.' (Inkata Press: Melbourne)

Parsons WT, Cuthbertson EG (2001) 'Noxious weeds of Australia.' 2nd edn. (CSIRO publishing: Collingwood, Victoria)

Department of Agriculture Government of Western Australia (2004) 'Weeds, pests and diseases' www.agric.wa.gov.au

Department of Primary Industries, Water and Environment (2004) 'Saffron thistle (Carthamus lanatus L.)' www.dpiwe.tas.gov.au

 

Prepared by Kylie Pethybridge, 2005

Checked by Carole Campbell, 2005

Updated by Justin KY Chu, July 2005

Checked by Dr Peter Michael, July 2005