Saffron thistle (Carthamus lanatus)
Saffron thistle is a very spiny plant with yellow flowers. It is a weed in pastures and crops.
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How does this weed affect you?
Saffron thistle is the most abundant thistle in southern Australia. It
- reduces yields and contaminates crops (such as wheat and other cereals)
- competes with pasture, especially on soils with low fertility, reducing productivity
- can injure eyes and mouths of livestock
- reduces wool quality
- restricts movement of people and livestock
- invades degraded open native vegetation and disturbed sites.
What does it look like?
Saffron thistle is an erect, annual herb usually up to 1 m tall. Seeds germinate in autumn and early winter. Through winter the plants have a rosette of leaves close to the ground. A single robust stem emerges in spring.
Leaves:
Rosette leaves are:
- are up to 20 cm long
- deeply divided and tipped with a short stout spine.
Stem leaves are:
- 3–6 cm long
- very rigid with short spines
- prominently veined
- wrapped around the stem at the base
- alternate.
Flowerheads are:
- yellow–cream with dark veins
- 10–20 mm wide and 20–25 mm long
- rigid and have a spine on the tip
- surrounded by many spiny leaf-like bracts
- mainly present late spring to early summer.
Seeds are:
- cream to brown or grey brown with dark blotches
- flattened with four ribs and a hook at the base
- 5–8 mm long
- usually tipped with a tuft of bristles 7–10 mm long.
Stems are:
- white, very pale yellow or pale green
- covered in cobweb-like hairs
- rigid
- ribbed along the stem.
Similar looking plants
Saffron thistle, soldier thistle, and glaucous star thistle may look very similar, and have similar impact. Saffron thistle is the most common.
- Glaucous star thistle (Carthamus leucocaulos) has purple flower heads.
- Soldier thistle (Picnomon acarna) has smaller flowers that are pink-purple, and arranged in clusters.
Where is it found?
Saffron thistle is widespread across NSW and more common west of the Great Dividing Range.
It is native to the Mediterranean region and Western Asia.
What type of environment does it grow in?
Saffron thistle grows in subtropical semi-arid and warm temperate climates. It is most common in areas that have 300 - 600 mm of annual rainfall. It can tolerate low temperatures.
Saffron thistle can tolerate a wide variety of soil types. It is more commonly found on poor soils because there is less competition from other ground covers. It is more abundant after wet springs.
Saffron thistle grows well on disturbed sites. It grows in:
- poor or overgrazed pastures
- cultivated land
- disturbed areas such as along roadsides, abandoned and degraded areas
- woodlands and native grasslands.
How does it spread?
By seed
Seed production varies greatly between plants. Each plant can produce over 200 seeds and the seeds can remain dormant for up to 8 years. Plants usually germinate in autumn. Seeds ripen around the same time as winter crops are ripening. Most seeds fall to the ground close to the parent plant. However, seed is also spread longer distances by:
- strong wind
- contaminated hay, grain
- attaching to wool, animals, vehicles and machinery.
References
Grace, B., Sindel, B.M., Sheppard, A.W., & Whalley, R.D.B. (1999, September). Ecology and management of saffron thistle (Carthamus lanatus L.) in New South Wales pastures. In Proceedings of the 12th Australian Weeds Conference, Hobart (pp. 13-15).
Grace, B.S., Whalley, R.D.B., Sheppard, A.W., & Sindel, B.M. (2002). Managing saffron thistle in pastures with strategic grazing. The Rangeland Journal, 24(2), 313-325.
James, T.J., Popay, I., Champion, P., Grbavac, N. and Rhode, B. (2012). An Illustrated Guide to Weed Seeds of New Zealand: New Zealand Plant Protection Society.
Kleinscmidt, H.E. & Johnson, R. W. (1977). Weeds of Queensland. Queensland Department of Primary Industries, Brisbane.
Morin, L & Sheppard, A. W. (2012). Carthamus lanatus L – saffron thistle. In J. Cullen, M. Julien & R. McFadyen (Eds), Biological control of weeds in Australia. CSIRO Publishing.
Pearce, J. R. (1995) Carthamus lanatus L. In R.H. Groves, R.C.H. Shepherd, & R.G. Richardson, (Eds) The Biology of Australian Weeds. RG and FJ Richardson. Melbourne.
PlantNET (The NSW Plant Information Network System). Royal Botanic Gardens and Domain Trust, Sydney. Retrieved 26 July 2021 from: https://plantnet.rbgsyd.nsw.gov.au/cgi-bin/NSWfl.pl?page=nswfl&lvl=sp&name=Carthamus~lanatus
More information
Control
Successful weed control relies on follow-up after the initial efforts. This means looking for and killing regrowth or new plants. Using a combination of control methods is usually more successful.
Prevention
Avoid buying contaminated fodder or seed that may have saffron thistle seed present. Clean machinery and vehicles that have been in areas with thistles before moving to clean areas.
Physical removal
Small plants can be dug out by hand or chipped out. If there are only a small number of scattered flowering plants they can be dug out, as once flowering they will not be susceptible to herbicides. Wear protective clothing and gloves to avoid injury from the spines.
Slashing
Mowing, cutting or slashing can prevent seed production if it is done just before flowering. Plants can regrow if this is carried out too early. Do not slash after seed is produced as this will spread the infestation.
Cultivation
A shallow cultivation or knockdown herbicides applied at or immediately prior to sowing the crop will destroy most seedlings.
Grazing and pasture management
Planting and maintaining competitive pastures can reduce the population of seedlings and newly emerged plants. Crash grazing while plants are bolting can reduce seed production.
Chemical control
Spraying
Apply to actively growing plants. Check the label for the recommended growth stage e.g. seedling or rosette. Thoroughly cover all of the leaves with herbicide.
Herbicide options
WARNING - ALWAYS READ THE LABEL
Users of agricultural or veterinary chemical products must always read the label and any permit, before using the product, and strictly comply with the directions on the label and the conditions of any permit. Users are not absolved from compliance with the directions on the label or the conditions of the permit by reason of any statement made or not made in this information. To view permits or product labels go to the Australian Pesticides and Veterinary Medicines Authority website www.apvma.gov.au
Users of agricultural or veterinary chemical products must always read the label and any permit, before using the product, and strictly comply with the directions on the label and the conditions of any permit. Users are not absolved from compliance with the directions on the label or the conditions of the permit by reason of any statement made or not made in this information. To view permits or product labels go to the Australian Pesticides and Veterinary Medicines Authority website www.apvma.gov.au
See Using herbicides for more information.
2,4-D 300 g/L + Picloram 75 g/L
(Tordon® 75-D)
Rate: 300 mL/ha
Comments: Boom spray application for young rosette or seedling plants.
Withholding period: Do not graze or cut crops (except sugar cane 8 weeks) or pastures for stock food for 7 days after application.
Herbicide group: 4 (previously group I), Disruptors of plant cell growth (Auxin mimics)
Resistance risk: Moderate
2,4-D amine 625 g/L
(Various products)
Rate: 110–170 mL per 150 L of water
Comments: High volume spot spray application.
Withholding period: 7 days withholding for grazing
Herbicide group: 4 (previously group I), Disruptors of plant cell growth (Auxin mimics)
Resistance risk: Moderate
2,4-D amine 625 g/L
(Various products)
Rate: 1.1–1.7 L/ha
Comments: Boom application, apply when in rosette stage.
Withholding period: 7 days withholding for grazing
Herbicide group: 4 (previously group I), Disruptors of plant cell growth (Auxin mimics)
Resistance risk: Moderate
2,4-D LV ester 680g/L
(Estercide® Xtra)
Rate: 800 mL to 2.5 L per ha
Comments: Boom spray application up to rosette stage
Withholding period: Do not graze or cut for stock food for 7 days after application.
Herbicide group: 4 (previously group I), Disruptors of plant cell growth (Auxin mimics)
Resistance risk: Moderate
Aminocyclopyrachlor 240 g/L
(Method® 240 SL)
Rate: 200-500 mL per 100 L of water
Comments: Spot spray with a handgun, hand-held sprayer or backpack sprayer. Thoroughly and uniformly wet the foliage but avoid spraying to the point of run off.
Withholding period: Nil for domestic grazing. See label for livestock export conditions.
Herbicide group: 4 (previously group I), Disruptors of plant cell growth (Auxin mimics)
Resistance risk: Moderate
Clopyralid 600 g/L
(Lontrel® Advanced )
Rate: 125 mL per 100 L water
Comments: Spot spray.
Withholding period: 7 days to 10 weeks see label for details.
Herbicide group: 4 (previously group I), Disruptors of plant cell growth (Auxin mimics)
Resistance risk: Moderate
Clopyralid 600 g/L
with MCPA 500 g/L (Various products)
Rate: 25 mL clopyralid per ha plus MCPA as per label
Comments: Boom spray. Actively growing rosettes; use higher rate on mature plants.
Withholding period: 7 days to 10 weeks see label for details.
Herbicide group: 4 (previously group I), Disruptors of plant cell growth (Auxin mimics)
Resistance risk: Moderate
Fluroxypyr 140 g/L + Aminopyralid 10 g/L
(Various products)
Rate: 500 mL in 100 L water
Comments: High volume hand gun application on actively growing plants.
Withholding period: Not required for pastures when used as directed. Do not graze or cut crops for stock food for 7 days after application. See label for export restrictions.
Herbicide group: 4 (previously group I), Disruptors of plant cell growth (Auxin mimics)
Resistance risk: Moderate
MCPA 340 g/L + Dicamba 80 g/L
(Kamba® M)
Rate: 80 mL per 15 L of water
Comments: For thistle seedlings. Spot spray from a knapsack. A repeat application may be necessary.
Withholding period: Do not graze or cut for stock food for 7 days after application.
Herbicide group: 4 (previously group I), Disruptors of plant cell growth (Auxin mimics)
Resistance risk: Moderate
MCPA 500 g/L
(Various products)
Rate: 100–200 mL in 150 L water
Comments: Spot spray.
Withholding period: Do not graze or cut for stock food for 7 days after application.
Herbicide group: 4 (previously group I), Disruptors of plant cell growth (Auxin mimics)
Resistance risk: Moderate
MCPA 500 g/L
(Various products)
Rate: 1–2 L/ha
Comments: Boom spray. Apply when in rosette stage. Use higher rate for larger weeds.
Withholding period: Do not graze or cut for stock food for 7 days after application.
Herbicide group: 4 (previously group I), Disruptors of plant cell growth (Auxin mimics)
Resistance risk: Moderate
Biosecurity duty
The content provided here is for information purposes only and is taken from the NSW Biosecurity Act 2015 and its subordinate legislation, and the Regional Strategic Weed Management Plans (published by each Local Land Services region in NSW). It describes the state and regional priorities for weeds in New South Wales, Australia.
| Area | Duty |
|---|---|
| All of NSW | General Biosecurity Duty All pest plants are regulated with a general biosecurity duty to prevent, eliminate or minimise any biosecurity risk they may pose. Any person who deals with any plant, who knows (or ought to know) of any biosecurity risk, has a duty to ensure the risk is prevented, eliminated or minimised, so far as is reasonably practicable. |
For technical advice and assistance with identification please contact your local council weeds officer.
Reviewed 2025
