Identification and Reproduction

Identification: 

• Maltese starthistle, also known as Malta starthistle can grow up to 0.7 m tall. 
• Stems are erect, winged, ridged and branched. 
• It produces lance-shaped leaves that are toothed and spiny hairs. With maturity hairs will appear cobwebby. 
• Flowers appear solitary or in clusters of 2-5 at the end of branches. Short disc flowers are bright yellow and encased in straw coloured bracts bearing spines. 
• Flowers bloom from July and September, seeds ripen by October. 

Reproduction: 

• Reproduces by seed. 
• Often transported by hitching a ride on humans, livestock and contaminating soil, crop seed and hay. 

Habitat & Ecology

• Usually invades open, disturbed areas such as roadsides, rangelands, pasutres and cultivated fields. 
• Adapted to all soil textures and nutrient poor sites. 
• It is shade intolerant but drought tolerant. 
• This plant is prone to taking over recently burned sites. 

Impacts

Social: 

• Common contaminant of cereal grains. 
• Also known to contaminate wool harvests. 
• Displaces native foraging species. 
• Can cause injury to grazing livestock as they are covered in spines. 

Ecological: 

• When found in large infestations with deplete water sources and natives species will experience droughty conditions. 

Management

Prevention is a high priority for this plant. 

• Please report this weed if you think you have seen it. 
• Thoroughly clean clothing, livestock, equipment and vehicles after traveling through an infested site. 
• Use certified hay, straw, mulch and seed mixtures. 

Resources

For more details check out the Invasive Species Compendium datasheet on Centaurea melitensis. 

The United States Department of Agriculture provides a Field Guide for Managing Malta Starthistle in the Southwest here. Please note that this is a US resource and Canadian guidelines and regulations may differ. Be sure to read labels prior to use. 

Header photo (Forest and Kim Starr).