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. 

Mechanical/Manual Control: 

• For small infestations hand pulling is effective. 
• Replant recently burned sites as soon as possible. 

Biological Control:

There are several agents being researched that may help suppress the growth and spread of maltese starthistle.  So far there have not been any successful results in controlling the weed. 

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).