Centaurea solstitialis, Yellow Starthistle

Gardens & Landscapes, Invasive Species, Extension Master Gardener February 23, 2012 Print Friendly and PDF

Invasive Species: Centaurea solstitialis, Yellow Starthistle

Yellow starthistle invades a wide variety of habitats. It is an annual that can grow from 0.25 to 3 ft. (0.1 to 1 m) in height. Leaves near the base are petiolate, dissected, 2 to 6 in. (5 to 15 cm) long, and usually absent at time of flowering. Leaves further up the stem are decurrent, entire, and 0.4 to 4 in. (1 to 10 cm) long. Flowering occurs from June to October, when yellow flowers appear in heads at the tips of the branches. Bracts that subtend the flower head have small clusters of spines and stout central spines that are 0.4 to 1 in. (10 to 25 mm) in length. Yellow starthistle has two types of fruits or achenes. Most are cream to tan with a white pappus or plume; achenes in the outer ring are darker and lack a pappus. Yellow starthistle was accidentally introduced in the United States in the mid-1800s as contaminate of alfalfa seed. Yellow starthistle invades woodlands, pastures, roadsides, and fields. Yellow starthistle is poisonous to horses and can be fatal.

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


Taxonomy: Scientific and Common Names for This Species

Asterales > Asteraceae > Centaurea solstitialis L.

Synonym(s): yellow star thistle, yellow star-thistle

Centaurea solstitialis - USDA PLANTS Profile

Distribution Maps

yellow 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 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.

County Extension Offices - Find your county 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

Yellow starthistle is an annual that can grow from 0.25 to 3 ft. (0.1 to 1 m) in height.

Steve Dewey, Utah State University, bugwood.org Steve Dewey, Utah State University,  bugwood.org

Foliage

Leaves near the base are petiolate, dissected, 2 to 6 in. (5 to 15 cm) long, and usually absent at time of flowering. Leaves further up the stem are decurrent, entire, and 0.4 to 4 in. (1 to 10 cm) long.

Mary Ellen (Mel) Harte, bugwood.org Mary Ellen (Mel) Harte,  bugwood.org

Flower

Flowering occurs from June to October, when yellow flowers appear in heads at the tips of the branches. Bracts that subtend the flower head have small clusters of spines and stout central spines that are 0.4 to 1 in. (10 to 25 mm) in length.

Cindy Roche,  bugwood.org Mary Ellen (Mel) Harte,  bugwood.org

Fruit

Yellow starthistle has two types of fruits or achenes. Most are cream to tan with a white pappus or plume; achenes in the outer ring are darker and lack a pappus.

   
bugwood.org bugwood.org

Native Centaurea Species Resemble Yellow Starthistle

 

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

Karan A. Rawlins, University of Georgia, bugwood.org Karan A. Rawlins, University of Georgia, bugwood.org

 

- Images at invasive.org

   
bugwood.org bugwood.org

 

Additional Images for Yellow Starthistle

yellow starthistle - Images at invasive.org

 

Learning Resources for Yellow 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.

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

Biology and Biological Control of Yellow Starthistle - USDA Forest Service

Weeds Gone Wild: Alien Plant Invaders of Natural Areas - Plant Conservation Alliance

Element Stewardship Abstract - The Nature Conservancy

Weed of the Week - USDA Forest Service

Centaurea solstitialis, Yellow Starthistle - Fire Effects Information System

Noxious Weed Management Program - Colorado Department of Agriculture

Invasives Database - TexasInvasives.org

Invasive Plants of California's Wildland - California Invasive Plant Council

Global Invasive Species Database - Invasive Species Specialist Group


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