Centaurea calcitrapa, Purple Starthistle

Gardens & Landscapes, Invasive Species, Extension Master Gardener December 15, 2015 Print Friendly and PDF

Invasive Species: Centaurea calcitrapa, Purple Starthistle

Purple starthistle is a biennial to perennial invasive plant. It grows 2 to 3 ft. (0.6 to 0.9 m) tall. The stems and leaves are covered with fine hairs. Lower and basal leaves are divided or deeply lobed. Leaves become less divided toward the apex of the plant. Flowering occurs from July to October, when purple to pink blooms develop at the ends of the stems. Floral bracts are tipped with 1 in. (2.5 cm) long, straw-colored spines. Fruit are achenes that are about 1/8 in. (2.5 to 3.5 mm) long; white or brown streaked; and smooth without a pappus. A native of southern Europe, purple starthistle produces prolific seeds and often invades floodplains, dry forests, and grasslands. This plant is common in many western states and may occasionally be found in some midwestern and mid-Atlantic states.

What are invasive species and why should we be concerned about them? 


Taxonomy: Scientific and Common Names for This Species

Asterales > Asteraceae > Centaurea calcitrapa L.

Synonym(s): red starthistle

Centaurea calcitrapa - USDA PLANTS Profile

Distribution Maps

Purple starthistle - The reported distribution of this invasive species across the United States. (Source: Invasive Plant Atlas of the United States)

Up-to-the-minute distribution maps and why they are important

Reporting This Invasive Species

What is the best way and place to report the occurrence of an invasive species? 

 How to report an invasive species sighting to EDDMapS - Early Detection & Distribution Mapping System

EDDMapS - Report an invasive species to EDDMapS

Cooperative Extension Offices - Find your local Cooperative Extension Office on this map provided by USDA

How to Identify

This invasive species can be identified by looking for the characteristics described in the paragraphs that follow.

Plant

Purple starthistle is a biennial to invasive perennial plant that grows 2 to 3 ft. (0.6 to 0.9 m) tall. The stems are covered with fine hairs.

purple starthistle purple starthistle
Barry Rice, sarracenia.com, bugwood.org Malcolm Storey, BioImages - Virtual Field-Guide, bugwood.org

Foliage

Lower and basal leaves are divided or deeply lobed. Leaves become less divided toward the apex of the plant. The leaves are covered with fine hairs.

purple starthistle purple starthistle
Malcolm Storey, BioImages - Virtual Field-Guide, bugwood.org Steve Dewey, Utah State University, bugwood.org

Flower

Flowering occurs from July to October, when purple to pink blooms develop at the ends of the stems. Floral bracts are tipped with 1 in. (2.5 cm) long, straw-colored spines. 

purple starthistle purple starthistle
Barry Rice, sarracenia.com, bugwood.org Joseph M. DiTomaso, University of California - Davis, bugwood.org

Fruit

Fruit are achenes that are about 1/8 in. (2.5-3.5 mm) long; white or brown streaked; and smooth without a pappus.

purple starthistle purple starthistle
Barry Rice, sarracenia.com, bugwood.org D. Walters and C. Southwick, CPHST, bugwood.org

Native Centaurea Species That Resemble Purple Starthistle

 

Centaurea americana, American star-thistle - Images at invasive.org

American star-thistle (Centaurea americana) American star-thistle (Centaurea americana)
Karan A. Rawlins, University of Georgia,  bugwood.org Karan A. Rawlins, University of Georgia,  bugwood.org

 

Vernonia gigantea, tall ironweed - Images at invasive.org

tall ironweed tall ironweed

Bruce Ackley, The Ohio State University,
bugwood.org

Bruce Ackley, The Ohio State University,
bugwood.org

 

Additional Images for Purple Starthistle

Purple starthistle - Images at Invasive.org

 

Learning Resources for Purple Starthistle

 

Additional Information, Biology, Control and Management Resources

Control and management recommendations vary according to individual circumstances. Location, habitat, weather, and a variety of other conditions are factors that help determine the best treatment choice. To find the safest and most effective treatment for your situation, consult your state's land-grant institution. If you will use chemicals as part of the control process, always refer to the product label.

Unied States Land-Grant University System - Find your land-grant university's College of Agriculture, Cooperative Extension Service, or other related partner on this map provided by USDA.

Plant Profiles - Cal-IPC

Noxious Weeds - King County

Invasive Plant Management - Cal-IPC

Noxious Weed Control - ODA Plant Division

Invasive.org - Center for Invasive Species and Ecosystem Health

Jepson Herbarium - University of California


 

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This work is supported by the USDA National Institute of Food and Agriculture, New Technologies for Ag Extension project.