SafePlants

Spotted Knapweed: An Overview

Spotted knapweed is an invasive plant that has become a significant concern in various regions. This page provides information about its identification, distribution, ecological impact, and other relevant facts.

Considerations for Pets

• The plant is hairy and rough, which may cause skin irritation in sensitive animals.
• Spotted knapweed spreads by seed, and these seeds can remain dormant for up to 5 years, which could potentially lead to accidental ingestion by pets during outdoor activities.

Considerations for Children

• The plant is hairy and rough, which may cause skin irritation in sensitive children.

Scientific Name and Common Names

• Scientific Name: Centaurea stoebe L. subsp. micranthos (Gugler) Hayek
• Common Names: Spotted knapweed
• Another scientific name: Centaurea maculosa
• Synonyms: Centaurea biebersteinii

Taxonomy and Nomenclature

• Family: Asteraceae (Sunflower Family)
• Genus: Centaurea
• Taxonomic Rank: Subspecies
• Synonyms: Centaurea stoebe L. subsp. micranthos (Gugler) Hayek

Distribution and Habitat

• Native to Europe and western Asia, specifically central and southeast Europe, northern Italy, and central regions.
• Now widely distributed in North America, including the United States (especially the western United States, Great Lakes region, Montana, Idaho, central and eastern Oregon, Arkansas Ozarks, Wisconsin) and Canada.
• Thrives in a wide range of climate and soil conditions.
• Found in various habitats, including barrens, fields, forests, prairies, meadows, pastures, rangelands, and dry pastures, valleys, southeast facing dry slopes, sandy sites of low productivity, including grasslands.

Ecological Role

• Considered an aggressive, introduced weed species and an exotic invasive plant.
• Spreads quickly and can outcompete native vegetation.
• Infestations can reduce productivity of rangelands and increase production costs for ranchers.
• Can displace native plant communities and even outcompete other invasive species.

Morphological Characteristics and Growth Habits

• Biennial or short-lived perennial herbaceous plant.
• Grows to a height of 2 to 4 feet.
• Has a strong taproot and lateral roots.
• Hairy and rough texture.
• Each plant has from 1 to 15 stems.
• Alternate, pale leaves.
• Blooms from July through August.
• Bolts (grows long stems from the basal rosette of leaves) in early May.
• A prolific seed producer, growing up to 900 seeds per plant annually that are viable for up to 8 years.

Interactions with Other Organisms

• Subject to the effects of seed head-attacking biological control agents.
• Adult root-boring weevils (Cyphocleonus achates) can be found on spotted knapweed flower heads.
• Can be used as a livestock forage

Quirky Facts

• The name "Knapweed" is derived from the Anglo-Saxon word "cnaep," meaning top, knob, or button, referring to the flower bud.

Further Information

• Center for Invasive Species and Ecosystem Health.
• Tropicos database.
• abinvasives.ca
• The Nature Conservancy’s Element Stewardship Abstracts (ESAs).