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yellow star-thistle
Scientific Name: Centaurea solstitialis
Family: Asteraceae
Category: Dicot
Growth: Forb/herb
Duration: Annual
Other Names:
Yellow Starthistle (Centaurea solstitialis)
Yellow starthistle is an invasive annual plant known for its bright yellow flowers and widespread presence in disturbed areas. Understanding its characteristics and spread is crucial for managing its impact.
Considerations for Pets
- The text explicitly mentions, "Yellow starthistle is a plant that you don't want your horse to tangle with," suggesting potential harm to horses.
Considerations for Children
- The plant features "sharp spines" surrounding the base of the flowers, potentially posing a risk of injury.
Scientific Name and Common Names
- Scientific Name: Centaurea solstitialis L.
- Common Names: Yellow star thistle, geeldissel, golden star thistle, St. Barnaby's thistle, yellow centaury, yellow cockspur, Barnaby's thistle.
Taxonomy and Nomenclature
- Family: Asteraceae (Compositae)
- Genus: Centaurea L.
- Species: Centaurea solstitialis L.
- Synonyms: Barnaby's thistle, Centaurea solstitialis.
- Related to other knapweeds and starthistles.
Distribution and Habitat
- Native to the Mediterranean Basin region, Africa, temperate Asia, and Eurasia (Balkan-Asia Minor, the Middle East and south-central Europe).
- Found in disturbed areas such as roadsides, abandoned fields, and waste areas.
- Has spread to California, other western states in the USA, and even been found in limited locations in Colorado.
Ecological Role
- Considered an invasive species in many regions.
- Highly competitive and can form dense, impenetrable stands.
- In California, it is considered an invasive plant of wildlands.
- Impacts pasture and rangeland, particularly in northern Idaho.
Morphological Characteristics and Growth Habits
- Long-lived winter annual, occasionally a biennial broadleaf plant.
- Grows 20 to 80 cm tall (18 to 36 inches). Can range from 10 inches to over 6 feet in height depending on growing conditions.
- Deep taproot.
- Winged stems.
- Silvery-green when young, gray-green later in the season.
- Produces one to many yellow flower heads at the tips of branches.
- Flowerheads are ovoid and spiny.
- Flowers are bright yellow with tubular florets and sharp spines surrounding the base.
- Spreads exclusively by seed, which may lie dormant for as long as 10 years.
- Bolts from May to June, producing spiny flower heads.
Interactions with Other Organisms
- Seeds can hitchhike by "jabbing spines" into passing animal hide or clothing.
- Subject to biological control efforts, including the use of Chaetorellia australis (Diptera: Tephritidae).
- Competition with native broadleaf plants.
Further Information
- University of California guidelines for control of Yellow Starthistle.
- Center for Invasive Species and Ecosystem Health.
- Invasive Plants of California's Wildlands.
- USDA Forest Service Weeds Gone Wild.
- Field Guide for Managing Yellow Starthistle in the Southwest.