--- title: Thistles canonical: https://fernland.com.au/problem-solver/thistles/ dateModified: 2026-08-07 09:39:13 summary: "Identify thistles, spiny broadleaf weeds from the Cirsium, Carduus and Onopordum genera. Learn where they establish, how to recognise rosettes, stems, flowers and seed, and why early management before flowering is important." type: article keywords: [Thistles, "Various Genera: Primarily Cirsium, Carduus, and Onopordum"] --- # Thistles > Identify thistles, spiny broadleaf weeds from the Cirsium, Carduus and Onopordum genera. Learn where they establish, how to recognise rosettes, stems, flowers and seed, and why early management before flowering is important. *Various Genera: Primarily Cirsium, Carduus, and Onopordum* Thistles are a large group of spiny broadleaf weeds within the daisy family (Asteraceae), commonly grouped under genera such as *Cirsium* (e.g. Scotch thistle, spear thistle, Californian thistle), *Carduus* (e.g. slender/nodding thistle, saffron thistle relatives) and *Onopordum* (cotton thistle, Illyrian thistle). While the species differ in detail, most share a rosette-forming habit, spine-tipped leaves and a purple, yellow or pink flower head enclosed by spiny bracts. Seedlings emerge as a flat rosette of lobed, often waxy or hairy leaves with spines along the margins. As the plant matures it either stays as a low rosette (stemless or biennial types) or sends up an erect, ribbed or winged flowering stem up to 1–2 m tall, depending on species. Leaves are typically deeply lobed or toothed, dull green to greyish, and armed with sharp spines at the lobe tips. Flower heads are rounded or globular, surrounded by rows of spiny bracts, and range from purple-pink (most *Cirsium* and *Carduus*) to yellow (star thistle, saffron thistle). Flowering is followed by masses of wind-dispersed seed carried on a tuft of fine hairs (pappus), giving the familiar thistledown. Root systems vary from simple taproots in annual/biennial species to extensive creeping lateral roots in perennial species such as Californian thistle, which allows regrowth from root fragments. Thistles occur across most of temperate and southern Australia, including pastures, roadsides, disturbed ground, crop margins and neglected turf or landscape areas. Annual and biennial species typically germinate with autumn or winter rains, forming rosettes over winter and flowering in spring to early summer; perennial species can persist year-round via their root systems and regrow after mowing or slashing. Management relies on preventing seed set, since most species spread prolifically by wind-blown seed, and on exhausting root reserves in perennial types through repeated cultivation, slashing or targeted herbicide use at the rosette to early bud stage. Good pasture, turf or garden bed competition and prompt control of scattered plants before flowering reduce long-term infestations. ## How to identify - Spiny rosettes appearing in pastures, turf edges, garden beds or disturbed soil, often in patches on bare or overgrazed ground. - Erect, spine-covered stems developing from rosettes, topped with purple, pink or yellow globular flower heads enclosed in spiny bracts. - Dense stands reducing pasture or turf usability, causing injury to stock, mowing equipment and workers, and shading out desirable species. - Fluffy, wind-borne seed heads (thistledown) present after flowering, indicating imminent seed spread. - For perennial types such as Californian thistle, scattered shoots reappearing in the same area after slashing or shallow cultivation, arising from an extensive creeping root system rather than seed.**Field check:** Dig around a suspect plant to check root type — a single taproot suggests an annual or biennial species, while a network of pale, cord-like lateral roots indicates a perennial thistle capable of regrowing from root fragments. **Lookalikes:** Spiny sowthistles (*Sonchus* spp.) resemble true thistles but have softer, less rigid spines, hollow stems that exude milky sap when cut, and smaller yellow dandelion-like flowers rather than the tufted globular heads of *Cirsium*, *Carduus* and *Onopordum*. Correct identification matters because control timing and herbicide susceptibility can differ between these groups. ## Registered products we stock - [Freehand Pre-emergent Herbicide](https://fernland.com.au/freehand-pre-emergent-herbicide/) — BASF - [Barricade Pre-Emergent Herbicide](https://fernland.com.au/barricade-pre-emergent-herbicide/) — Syngenta - [Dicamba M Selective Herbicide](https://fernland.com.au/dicamba-m-selective-herbicide/) — PCT SureFire - [DISMISS Granular Ornamental Pre-emergent Herbicide](https://fernland.com.au/dismiss-granular-ornamental-pre-emergent-herbicide/) — Macspred - [Multi Turf | Selective Herbicide](https://fernland.com.au/multi-turf-selective-herbicide/) — PCT SureFire - [Ronstar Pre-emergent Herbicide for Turf & Ornamentals](https://fernland.com.au/ronstar-pre-emergent-herbicide-for-turf-ornamentals/) — Envu - [Vigilant II Herbicide Gel - Applicator Pack](https://fernland.com.au/vigilant-ii-herbicide-gel-applicator-pack/) — Corteva - [Associate Herbicide](https://fernland.com.au/associate-herbicide/) — Nufarm - [Metsulfuron Methyl Herbicide](https://fernland.com.au/metsulfuron-methyl-herbicide/) — PCT SureFire - [Monument Liquid Turf Herbicide](https://fernland.com.au/monument-liquid-turf-herbicide/) — Syngenta - [Buffalo - Bindii & Broadleaf Weedkiller Herbicide](https://fernland.com.au/buffalo-bindii-broadleaf-herbicide/) — PCT SureFire - [Barricade HG | Pre-Emergent Herbicide | 250mL](https://fernland.com.au/barricade-hg-pre-emergent-herbicide-250ml/) — Syngenta - [Raizon Herbicide](https://fernland.com.au/raizon-herbicide/) — PCT SureFire - [Amicide Advance 700 Selective Herbicide](https://fernland.com.au/amicide-advance-700-selective-herbicide/) — Nufarm - [Casper Turf Herbicide](https://fernland.com.au/casper-turf-herbicide/) — Syngenta - [Quali-Pro Nutmeg | Selective Herbicide](https://fernland.com.au/quali-pro-nutmeg-selective-herbicide/) — Adama - [Fairway Selective Herbicide](https://fernland.com.au/fairway-selective-herbicide/) — Adama - [Metmac 600 Herbicide](https://fernland.com.au/metmac-600-herbicide/) — Macspred - [Destiny Selective Turf Herbicide](https://fernland.com.au/destiny-selective-turf-herbicide/) — Envu - [Lonhro 100WG Turf Herbicide](https://fernland.com.au/lonhro-100wg-turf-herbicide/) — Colin Campbell Chemicals - [Starane Advanced | Broadleaf Herbicide](https://fernland.com.au/starane-advanced-broadleaf-herbicide/) — Corteva - [Rox.Star 200 | Herbicide](https://fernland.com.au/rox-star-200-herbicide/) — Kendon - [Stature 3-Way Broadleaf Turf Herbicide](https://fernland.com.au/stature-3-way-broadleaf-turf-herbicide/) — Colin Campbell Chemicals - [Trimac Industrial Herbicide](https://fernland.com.au/trimac-industrial-herbicide/) — Macspred - [Crucial Herbicide](https://fernland.com.au/crucial-herbicide/) — Nufarm - [Weedmaster Duo Glyphosate 360 Herbicide](https://fernland.com.au/weedmaster-duo-glyphosate-360-herbicide/) — Nufarm - [Glyphosate Weedpro 360 Bio Aqua Herbicide](https://fernland.com.au/glyphosate-weedpro-360-bio-aqua-herbicide/) — PCT SureFire - [Glyphosate 360 Herbicide](https://fernland.com.au/glyphosate-360-herbicide/) — PCT SureFire - [Glyphosate Weedpro 540 Bio Herbicide](https://fernland.com.au/glyphosate-weedpro-540-bio-herbicide/) — PCT SureFire - [Weedmaster DST Herbicide](https://fernland.com.au/weedmaster-dst-herbicide/) — Nufarm - [Gamma | Herbicide](https://fernland.com.au/gamma-herbicide/) — PCT SureFire - [Arsenal Super Herbicide](https://fernland.com.au/arsenal-super-herbicide/) — BASF - [Roundup Advance Green Concentrate CRC](https://fernland.com.au/roundup-advance-green-concentrate-crc/) — Roundup ## Image credits - [Photo: Sciadopitys from UK via Wikimedia Commons (CC BY-SA 2.0)](https://commons.wikimedia.org/wiki/File:Cirsium_vulgare_Harthope.jpg) - [Photo: AnRo0002 via Wikimedia Commons (CC0)](https://commons.wikimedia.org/wiki/File:20170531Cirsium_vulgare2.jpg) - [Photo: AnRo0002 via Wikimedia Commons (CC0)](https://commons.wikimedia.org/wiki/File:20110715Cirsium_vulgare.jpg) - [Photo: AnRo0002 via Wikimedia Commons (CC0)](https://commons.wikimedia.org/wiki/File:20130727Cirsium_vulgare1.jpg)