Spotted knapweed

Discuss this plant with the guide — choose this profile as a possible match and prepare your observations for Colorado Plants & Practical Care.

Centaurea stoebe

Colorado noxious weed · List B — Stop the spread. J-spotted-knapweed

Established in some areas. Requirements vary by location: eradication, containment or suppression to stop further spread. This is a management category, separate from danger ratings. Category source · What the lists mean.

Competes with native vegetation. Native status, garden use and noxious-weed class are separate from toxicity. Exposure help.

Identification caveat: Some Colorado references use Centaurea maculosa for spotted knapweed. We retain their name in the citation record and use C. stoebe as the catalog label.

Still researching this plant

This is a sourced working profile. Evidence is incomplete for People, Dogs & cats, Other animals. Identification and source-photo limits are explained below. Independent botanical and veterinary review is pending. Uncertainty is not a finding that the plant is safe.

Three views of this plant

Photos are source-identified examples, not a complete identification key. Check leaves, stems, flowers and fruit together. Locations are not assumed to be in Colorado.

Centaurea stoebe: Close view of the purple tubular florets forming a knapweed flower head. — **flower** — Close view of the purple tubular florets forming a knapweed flower head.
Alan Vernon · CC BY 2.0
Photo source and identification
Original record · Original image
Source page scientific identification plus visual morphology review of the selected photograph. This is a source-identified reference image, not a specimen-based taxonomic determination. Spotted knapweed is a species complex; North American invasive plants are often treated as C. stoebe subsp. micranthos. Some source photos retain the historically applied name Centaurea maculosa. Photographs do not establish subspecies or ploidy.
Wikimedia server-resized derivative; no crop, color change, or generative editing. Gallery display preserves the full image; the catalog preview uses a CSS crop.

Centaurea stoebe: Branched slender stems with divided narrow leaves and scattered purple flower heads. — **habit** — Branched slender stems with divided narrow leaves and scattered purple flower heads.
Agnieszka Kwiecień, Nova · CC BY-SA 4.0
Photo source and identification
Original record · Original image
Source page scientific identification plus visual morphology review of the selected photograph. This is a source-identified reference image, not a specimen-based taxonomic determination. Spotted knapweed is a species complex; North American invasive plants are often treated as C. stoebe subsp. micranthos. Some source photos retain the historically applied name Centaurea maculosa. Photographs do not establish subspecies or ploidy.
Wikimedia server-resized derivative; no crop, color change, or generative editing. Gallery display preserves the full image; the catalog preview uses a CSS crop.

Centaurea stoebe: Flower-head base showing overlapping bracts with dark fringed tips, beside an unopened head. — **involucral-bracts** — Flower-head base showing overlapping bracts with dark fringed tips, beside an unopened head.
Kristian Peters -- Fabelfroh 08:50, 2 November 2006 (UTC) · CC BY-SA 3.0
Photo source and identification
Original record · Original image
Source page scientific identification plus visual morphology review of the selected photograph. This is a source-identified reference image, not a specimen-based taxonomic determination. Spotted knapweed is a species complex; North American invasive plants are often treated as C. stoebe subsp. micranthos. Some source photos retain the historically applied name Centaurea maculosa. Photographs do not establish subspecies or ploidy.
Wikimedia server-resized derivative; no crop, color change, or generative editing. Gallery display preserves the full image; the catalog preview uses a CSS crop.

Recognize

Purple flowerheads with dark-tipped, fringed bracts; a short-lived perennial spreading mainly by seed. C-descriptions

Plants & habitat

An introduced noxious weed. Preventing seed production and maintaining desirable vegetation are parts of long-term control. J-spotted-knapweed

People

This review did not establish a species-specific human toxicity profile. This is an evidence gap, not proof of safety.

Dogs & cats

Species-specific ingestion effects and exposure thresholds were not established in the reviewed sources. This is an evidence gap, not proof of safety.

Other animals

Do not transfer Russian-knapweed horse toxicity to spotted knapweed without species-specific evidence. This is an evidence gap, not proof of safety.

Before taking action

Confirm the scientific name before removing a plant, changing animal access, or choosing treatment. An evidence gap means this review has not resolved the question. It does not mean safe. For listed weeds, consult your county weed program about the requirements for your location; follow the current label for any pesticide. S27

References

J-spotted-knapweed — Spotted Knapweed, Jefferson County, Colorado. Accessed 2026-09-07T00:27:26+00:00. Locator: Description, impacts, Colorado list designation, management.
C-descriptions — Weed descriptions, Colorado State University Extension. Accessed 2026-09-07T00:24:02+00:00. Locator: Species entries.

Content revised 2026-09-07 03:50:00Z · Source checks dated separately in the references.