Artichoke thistle (Cynara cardunculus)

Also known as: wild artichoke

Artichoke thistle has long prickly leaves and large blue-purple or sometimes pink flowers. It competes with pastures, crops and native plants.

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How does this weed affect you?

Artichoke thistle is an invasive weed that:

• outcompetes other plants by releasing chemicals into the soil that inhibit their growth.
• smothers pasture plants, reducing productivity
• competes with crops and can make harvesting difficult
• invades grasslands, open woodlands, and wetlands
• has spines that can restrict movement of wildlife and livestock.

Human health

Touching artichoke thistles can irritate and inflame the skin in some people. The spines can pierce the skin.

What does it look like?

Artichoke thistle is a perennial herb that grows up to 2 m tall. Seedlings grow slowly through winter. Plants have a rosette of grey-green leaves at the base which may die off over summer. New leaves grow in autumn and plants usually start to flower in their second summer.

 Leaves are:

• greyish-green and sparsely hairy on the upper surface
• whitish with dense, slightly sticky, cobweb-like hairs below
• usually up to 50 cm long and 35 cm wide but the rosette leaves at the base can be up to 90 cm long.
• deeply divided with many lobes with yellow-orange spines along the edges
• in a rosette at the base
• alternate along the upright stems.

Flowerheads are:

• dense, very spiny thistle heads, 5-13 cm in diameter
• flower bristles are blue-purple; sometimes whitish or pink; up to 5 cm long
• single, on thick stalks at the end of branches.

Seeds are:

• brown or black with streaks
• 6-8 mm long
• topped with white feathery hairs (pappus) up to 4 cm long.

Stems are:

• ribbed and sparsely covered in cobweb-like hairs
• branched at the top.

 There is usually one stem growing from a rosette. Occasionally rosettes have up to 8 stems.

Roots:

There is a large taproot up to 2m long.

Similar species:

Artichoke thistle looks similar to other introduced species:

• Globe artichoke (Cynara scolymus, sometimes referred as Cynara cardunculus subsp. Flavescens) is cultivar of artichoke thistle. The flowerheads of this cultivar do not have spiny bracts. Instead, they are fleshy and edible.
• Scotch thistle (Onopordum acanthium) which has spiny wings along the stems.
• Illyrian thistle (Onopordum illyricum) which has spiny wings and dark coloured spines.
• Spear thistle (Cirsium vulgare), which has dark green leaves that are white and wooly on the underside.

Where is it found?

In NSW, artichoke thistle is quite rare; it has mostly been found in the Riverina, Murray, Western and Central West Regions. It also grows in other regions including near the coast.

Artichoke thistle came into Australia as a garden plant; it is native to the Mediterranean region.

What type of environment does it grow in?

Artichoke thistles grow best in warm temperate regions with winter rainfall. Occasionally, they grow in sub-tropical and semi-arid climates. They usually grow in areas with fertile soils and 500–750 mm of rain per year.

Seedlings are sensitive to shade and grow much better in full sun.

Artichoke thistles are most common in pastures and along roadsides. They also grow in crops, grasslands, open woodlands, wetlands, riparian areas, gardens and disturbed sites.

How does it spread?

By seed

Each plant can produce up to 30,000 seeds per year. The seeds can be spread by the wind for up to 40 m, though most seeds fall within 6 m of the parent plant. Seeds are also spread by:

• moving water
• contaminated mud or soil
• sticking to animals including sheep cattle and birds
• dumping floral arrangements.

By plant parts

Plants also grow from root or crown fragments which can be spread by cultivation equipment.

References

Bean, A. R. (2015). Cynara cardunculus subsp. flavescens, Asteraceae Subfam. 2. Carduoideae Trib. 1. Cardueae. In A. J. G. E. Wilson (Ed.), Flora of Australia (Vol. 37, pp. 61– 62). Melbourne: CSIRO publishing.

Biosecurity Queensland (2016). Weeds of Australia: Cynara cardunculus. Retrieved 28 August 2020 from: https://keyserver.lucidcentral.org/weeds/data/media/Html/cynara_cardunculus.htm

Marushia, R. G., & Holt, J. S. (2006). The effects of habitat on dispersal patterns of an invasive thistle, Cynara cardunculus. Biological Invasions, 8(4), 577-594.

Marushia, R. G., & Holt, J. S. (2008). Reproductive strategy of an invasive thistle: effects of adults on seedling survival. Biological Invasions, 10(6), 913-924.

Parsons, W. T., Parsons, W. T., & Cuthbertson, E. G. (2001). Noxious weeds of Australia. CSIRO publishing.

Richardson, F. J., Richardson, R. G., & Shepherd, R. C. H. (2011). Weeds of the south-east: an identification guide for Australia (No. Ed. 2). CSIRO.

Uddin, M. N., Asaeda, T., Shampa, S. H., & Robinson, R. W. (2020). Allelopathy and its coevolutionary implications between native and non-native neighbors of invasive Cynara cardunculus L. Ecology and evolution, 10(14), 7463-7475.

White, V. A., & Holt, J. S. (2005). Competition of artichoke thistle (Cynara cardunculus) with native and exotic grassland species. Weed Science, 53(6), 826-833.

More information

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Control

Successful weed control relies on follow up after the initial efforts. This means looking for and killing regrowth or new seedlings. Using a combination of control methods is usually more successful.

Physical removal

By hand

Dig out small infestations or seedlings. Remove as much of the taproot as possible as the plant can regrow from cut roots. Dispose of plants so that they are not left touching the soil.

Pasture management

Sowing and maintaining healthy pasture can limit seedling growth, as artichoke thistle seedlings do not grow well when shaded.

Grazing

Goats will eat artichoke thistle flowers. Grazing goats can reduce flowering and seed production.

Cultivation

Cultivation can be effective if repeated regularly whenever new growth appears.

Chemical control

Spraying

Dicamba is most effective when applied in spring before the flowering stalk emerges.

Glyphosate is most effective when the plants are at the seedhead stage.

Herbicide options

See Using herbicides for more information.

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Dicamba 750 g/L (Kamba® 750)
Rate: 1.1 L/ha Use a minimum of 1500 L solution per ha. Add a surfactant.
Comments: Boom spray for non-crop situations. Spray prior to flowering.
Withholding period: Do not harvest, graze or cut for stock food for 7 days after application.
Herbicide group: I, Disruptors of plant cell growth (synthetic auxins)
Resistance risk: Moderate

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Dicamba 750 g/L (Kamba® 750)
Rate: 67 mL per 100 L of water. Add a surfactant.
Comments: Spray prior to flowering. For non crop situations.
Withholding period: Do not harvest, graze or cut for stock food for 7 days after application.
Herbicide group: I, Disruptors of plant cell growth (synthetic auxins)
Resistance risk: Moderate

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Dicamba 750 g/L (Kamba® 750)
Rate: 16 mL per 15 L of water. Add a surfactant.
Comments: Spot spray prior to flowering. For non-crop situations.
Withholding period: Do not harvest, graze or cut for stock food for 7 days after application.
Herbicide group: I, Disruptors of plant cell growth (synthetic auxins)
Resistance risk: Moderate

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Glyphosate 360 g/L (Various products)
Rate: 10 ml per 1 L water
Comments: Spot spray. For general weed control in domestic areas (home gardens), commercial, industrial and public service areas, agricultural buildings and other farm situations.
Withholding period: Nil.
Herbicide group: M, Inhibitors of EPSP synthase
Resistance risk: Moderate

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Glyphosate 360 g/L (Weedmaster Duo)
Rate: 75mL/15L water
Comments: Knapsack spray. Apply at the rosette-early head stage.
Withholding period: Nil.
Herbicide group: M, Inhibitors of EPSP synthase
Resistance risk: Moderate

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MCPA 250 g/L (MCPA 250)
Rate: 8.5 L/ha
Comments: For pastures and cereal crops. High volume, repeat following year. Add wetting agent.
Withholding period: Do not graze or cut for stock food for 7 days after application.
Herbicide group: I, Disruptors of plant cell growth (synthetic auxins)
Resistance risk: Moderate

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Biosecurity duty

The content provided here is for information purposes only and is taken from the 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 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.

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Reviewed 2021