Spear Thistle (Cirsium vulgare)
Spear Thistle, Black thistle or Bull Thistle, spreads quickly via wind blown seeds. It is an Autumn and Winter germinating biennial herb and has a two year life span. For more information, please check out our weed ID chart.
Spear Thistle is a good indicator weed of compaction, and heavy, acidic soils.
After you finish reading this, you will be able to:
- Identify Spear Thistle, Black Thistle or Bull Thistle.
- Know the habitat of Spear Thistle.
- Know the best cultural and chemical options to control Black Thistle.
Spear Thistle Identification.
Bull Thistle can quickly spread via wind blown seeds.
Category: This an Autumn and Winter biennial dicot.
Flower: Flowerheads are reddish to purple and 1.2 to 4 cm wide.
Leaves: The leaves of this thistle are dark green, rough and hairy on the upper surface. Each lobe terminates in a sharp rigid spine, and the leaves are deeply divided.
Height: It grows up to 60 to 120 cm, and sometimes up to 1.5 metres.
Reproduction: Bull Thistle only reproduces by seed, and can produce up to 8000 seeds per year. The seeds are short-lived on the soil surface, but can be dormant for many years in the soil.
Comments: At first Black Thistle grows as a rosette, 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: Bull Thistle is a common species of wet or Summer-moist land, including waste-land, pastures and high N soils. It prefers heavy soils, in direct sunlight with good fertility. It will tolerate slight to moderate salinity, and periodic waterlogging but does not survive prolonged flooding.
The seeds develop in the Autumn but if there is enough moisture they may grow at other times.
Seeds are spread by:
- Wind (though usually not very far)
- Moving water
- Sticking to animals, boots, or machinery and
- By seed.
How to remove Spear Thistle from your lawn.
Cultural control.
Spear Thistle is not a strong competitor in well maintained lawns and turf grass, and does not invade lawns that have good turf cover in the Summer and Autumn.
Repeated mowing before it flowers, as this reduces the population over time and prevents seed production. Be aware that mowing does not kill first year rosette. Hand removal works well if you cut the weed below the crown or the rosette of the plant, and it is important that the roots are dug up and you dispose of the flower stems off-site. This prevents them from forming viable seeds.
Chemical control.
Glyphosate and Dicamba herbicides work well on Bull Thistle, but be aware that Glyphosate is not selective and kills everything it comes into contact with.
2,4-D provides good top growth control on young 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.
