Spear Thistle (Cirsium vulgare)
Spear Thistle (Cirsium vulgare) or Bull Thistle, spreads quickly via wind blown seeds. It is a biennial herb that germinates in the Autumn and Winter, has a two year life span, and a taproot up to 70 cm long.
After you finish reading this, you will be able to:
- Identify the Spear Thistle (Cirsium vulgare) or Bull Thistle.
- Know the habitat of Spear Thistle.
- Know the best cultural and chemical options to control the Bull Thistle.
Why is Spear Thistle a Problem Weed?
- Spear thistle thrives in fertile soils and outcompetes desirable plants for water, nutrients, and sunlight.
- The sharp spines deter livestock from grazing, and makes them avoid areas with heavy infestations. This leads to overgrazing of other plants.
- The spines contaminate wool.
- Spear thistle produces numerous seeds that are easily dispersed by wind. This enables the weed to spread rapidly.
- It has a deep taproot and s able to survive in various soil conditions. This makes it dificult to eradicate completely.
- The flowers, stems and leaves of the Bull Thistle can irritate the skin upon contact, and cause redness and minor wounds.
For more information, please check out our weed ID chart.
The distribution map for Spear Thistle in Australia is courtesy of the Atlas of Living Australia.
Spear Thistle ( Cirsium vulgare) is a good indicator weed of compact, heavy, acidic soils.
How to Identify Spear Thistle.
The Spear or Bull Thistle spreads very quickly by wind blown seeds.
Category: This weed is an Autumn and Winter biennial dicot.
Photosynthetic Pathway: C3 Weed.
Flower: The flower heads of Spear Thistle are red to purple and 1.2 to 4 cm wide. In poor growing conditions, Spear Thistles can flower when they are only 30 cm tall.
Leaves: The dark green leaves of the Spear Thistle are rough and hairy on their upper surface. Each lobe terminates in a sharp rigid spine, and the leaves are deeply divided.
Height: Spear Thistle grows up to 60 to 120 cm, and sometimes reaches up to 1.5 metres.
Reproduction: Bull Thistle’s only reproduce by seed, and each plant can produce up to 8,000 seeds in a year. The seeds are short-lived on the soil surface, but can remain dormant for many years in the soil.
- Seed Longevity: >5 years.
- Weight: 2.5mg.
- Seeds/head or capsule: 100.
- No/plant: 8,000.
Comments: At first Spear Thistle grows as a rosette. Then as it matures, it produces upright branched spiny stems. The rosette leaves at the base of the plant are up to 30 cm long, and the stem leaves have no stalk and are 4–25 cm long.
Habitat: Spear Thistle is a common species of wet or Summer-moist land, waste-land, pastures and high N soils. It prefers heavy soils, in direct sunlight with good fertility. It tolerates some degree of salinity, and occasional waterlogging, but does not survive prolonged flooding.
The seeds of Cirsium vulgare develop in the Autumn, but if there is enough moisture they may grow at other times.
Spear Thistle seeds are spread by:
- Wind (though usually not very far).
- Moving water and
- Sticking to animals, boots, or machinery.
How to Remove Spear Thistle from your lawn.
Cultural control of Spear Thistle.
- Spear Thistle or the Bull Thistle is not a strong competitor. This means that well maintained lawns and turf areas tend not to have issues with Spear Thistles. This weed does not invade areas that have good turf cover in the Summer and Autumn.
- The basis of cultural control of this weed is to mow at the right height, fertilize appropriately, and water as and when required for the turf species present.
- If you mow regularly before Spear Thistle sets seed it will reduce the population over time, and prevent further seed production. However, be aware that even if you mow frequently this does not kill first year rosette.
- Hand removal of Spear Thistle works well (wear good gloves) if you cut the weed below the crown or the rosette of the plant.
- Make sure that you dig up all the roots, and you bag all vegetative material up. Its important that you then dispose of this material, and the flower stems off-site, as this prevents them from forming viable seeds.
Chemical Control of Spear Thistle.
- The most cost-effective way to control the Spear or Bull Thistle is to spray young thistles
- Thistles are still small in the Autumn and Winter so you get the best results if you spray then.
- You can spot spray in the Spring and Summer for larger Spear Thistles.
Management Calendar for Herbicide Treatment of Spear Thistle.
Management Calendar For Spear Thistle | ||||||||||||
Months | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec |
Germination | ||||||||||||
Flowering/Seeding | ||||||||||||
Herbicide Treatment | ||||||||||||
Post Emergent Herbicides for Spear Thistle.
- 2,4-D and MCPA provides good top growth control on young Spear Thistle plants before they flower. Spear Thistles in the rosette stage are very sensitive to herbicides when when you use these early in the growing season.
- Dicamba herbicides work well on larger Bull Thistles, but be aware that you cannot use this herbicide on Buffalo grass. Other options on larger thistles include Contra M, Weed Blast MA and Warhead Trio. The latter two are safe to use on Buffalo.
Table of Post Emergent Spear Thistle Herbicides.
Product | Active | Chemical Group | Rate/Ha | Comments |
2,4-D | 2,4-D | 4 | 1.8-3.2 L | Wet foliage thoroughly. DO NOT mow lawn for 1 week before and at least 1 weed after application. DO NOT use on Buffalo grass (WA only). |
Dicamba | Dicamba | 4 | 1.2L + 3.2L of 2,4-D Amine 625g/L | Use a minimum of 1000L/Ha water. Do not spray on Buffalo or Bent Grass. |
Contra M. | Dicamba + MCPA | 4 | 6.5 L | Apply in 250-400L water. DO NOT use on Buffalo grass. After use do not mow for 2 days before or after application or fertilize within two weeks. |
MCPA | MCPA | 4 | 930ml -1.8L | Apply in high volume to actively growing weeds. DO NOT mow for 2 days before application. Some transitory damage may occur to fine turf grasses |
Warhead | MCPA + Clopyralid + Diflufenican | 4 + 12 | 5 L | You may see discolouration on kikuyu, carpet grass and Queensland blue. Avoid overlapping. Use an NIS. |
Weed Blast MA | Bromoxynil + MCPA | 6 + 4 | 3-6 L | Apply in a minimum of 500L/Ha water. DO NOT mow for 2 days after treatment. |
Non Selective Control of Spear Thistle.
- Glufosinate-ammonium provides control for 4 to 6 weeks, but it regrows and recovers due to the limited movement of glufosinate.
- Glyphosate. You can use Glyphosate as to control Spear Thistle. If you use Glyphosate, and water quality is an issue then use ProForce Manta Ray.
The following are non-selective but also have a long term residual and stop re-growth of Spear Thistle.
- Renegade. Renegade stops the germination of Spear Thistle for up to 12 months, and reduces the need for multiple herbicide applications.
- Numchuk Quad. This gives effective post and pre emergent Bull Thistle control for up to 12 months.Cortex Duo.
- Cortex Duo gives a rapid knockdown of Spear Thistle, and residual control for up to 3 months. It is also safe to use around trees.
Table of Non Selective Herbicides for Spear Thistle.
Product | Active | Chemical Group | Rate/Ha |
Glufosinate 200 | Glufosinate-ammonium | 10 | 1-6L |
Rapid Fire 800 | Glyphosate | 9 | 0.9-1.35 Kg |
Numchuk Quad | Terbuthylazine + Glyphosate + Amitrole Oxyfluorfen | 5 + 9 + 34 + 14 | 20-25L |
Cortex Duo | Nonanoic Acid + Oxyfluorfen | 14 | 7L/1000L |
Renegade | Bromacil | 5 | 3.5-6.5Kg |
