Identification and Reproduction

Identification: 

• This thistle grows up to 1.3 m tall. It is very branched and can appear bushy. 
• Stems are hairless, grooved and covered in resin spots. 
• Leaves on the upper stem are small and simple while lower stem leaves are lobed.

• Stems and leaves are covered in fine, cobwebby hairs but will become smooth with maturity. 
• Each inflorescence contains 25-40 disk flowers per head. Flower bracts are green or straw-coloured depending on season and covered in sharp yellow spines. 
• Flowers are purple and bloom from July through September.  

Reproduction: 

Purple starthistle reproduces by seeds that can be viable for 3 years. 

Habitat & Ecology

• Well adapted to various soil types. 
• Slightly shade-intolerant. 
• Often found on fields, roadsides, exposed areas, grasslands, rangelands and recently logged sites. 

Impacts

Social:

• Reduces foliage availability and displaces native species. 
• Displaces desired crop species. 
• Unpalatable to livestock. 

Management

Prevention is a high priority for this plant.

• Thoroughly clean shoes, clothing, pets, equipment and vehicles when leaving an infested site. 
• Avoid transporting unknown soil and plant materials.

Mechanical/Manual Control: 

• Avoid mowing as this can stimulate regrowth of stems. 
• Hand-pulling or cutting can be effective for small patches. When cutting, sever roots at least 5 cm below the ground. 

Resources

For more information check out the Texas Invasive Species Institute page on Purple Star Thistle here. 

Header photo (Xemenendura)