Common cocklebur
Discuss this plant with the guide — choose this profile as a possible match and prepare your observations for Colorado Plants & Practical Care.
Xanthium strumarium
Common weed; not an A/B/C listing in the reviewed state rule. CO-rules-2025
Burs catch in fur; seedlings and seeds are hazardous. Exposure help.
Identification caveat: Xanthium strumarium is treated broadly by some sources and split into other taxa by others. Photographs retain their original source identifications. Native status and a local specimen’s exact taxon need separate review.
Still researching this plant
This is a sourced working profile. Evidence is incomplete for Dogs & cats. 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
Source-identified reference photographs; these are not a complete identification key. A source location outside Colorado does not establish local occurrence.
Franco Folini · CC BY 2.5
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. Cocklebur taxonomy varies by flora and Xanthium strumarium is often used broadly. Related X. orientale-group plants have historically been included. These are source-identified X. strumarium references; one bur is explicitly labeled sensu stricto. General foliage or habit does not independently resolve the complex or establish the identity of Colorado plants.
Wikimedia server-resized derivative; no crop, color change, or generative editing. Gallery display preserves the full image; the catalog preview uses a CSS crop.
Stan Shebs · 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. Cocklebur taxonomy varies by flora and Xanthium strumarium is often used broadly. Related X. orientale-group plants have historically been included. These are source-identified X. strumarium references; one bur is explicitly labeled sensu stricto. General foliage or habit does not independently resolve the complex or establish the identity of Colorado plants.
Wikimedia server-resized derivative; no crop, color change, or generative editing. Gallery display preserves the full image; the catalog preview uses a CSS crop.
Stefan.lefnaer · 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. Cocklebur taxonomy varies by flora and Xanthium strumarium is often used broadly. Related X. orientale-group plants have historically been included. These are source-identified X. strumarium references; one bur is explicitly labeled sensu stricto. General foliage or habit does not independently resolve the complex or establish the identity of Colorado plants.
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
A summer annual with rough, broad leaves and hard burs covered in hooked prickles. N-xanthium-strumarium
Plants & habitat
Can form colonies in fields and wet disturbed ground. Hooked burs move on animals and clothing. N-xanthium-strumarium
People
NC State flags human poisoning but provides primarily animal clinical descriptions. Do not infer a human dose or identical symptoms. N-xanthium-strumarium
Evidence scope: Source warning; human clinical detail limited.
Dogs & cats
Burs attach to fur and can cause contact problems. Animal ingestion warnings do not establish dog- or cat-specific thresholds; prevent chewing seedlings, seeds and burs. N-xanthium-strumarium
Evidence scope: Physical-risk inference and general animal warning.
Other animals
Seedling cotyledons and seeds are the principal ingestion concern. The source describes low blood sugar, weakness, spasms and potentially fatal poisoning. N-xanthium-strumarium
Before taking action
Confirm identification and the requirements of your county weed program. For chemical treatment, follow the current product label, including restrictions around animals and water. S27
References
- CO-rules-2025 — Colorado Noxious Weed Act rules, 8 CCR 1206-2, Colorado Secretary of State / Department of Agriculture. Accessed 2026-09-07T01:07:48+00:00. Locator: Parts 3.1, 4.1, 5.1; management provisions; effective May 15, 2025.
- N-xanthium-strumarium — xanthium strumarium — Plant Toolbox, NC State Extension. Accessed 2026-09-07T01:04:56+00:00. Locator: Description; Attributes; Problems; Poisonous to Humans.
- S27 — 2103 – Colorado Noxious Weeds, PlantTalk Colorado · CSU Extension. Accessed 2026-09-07T00:23:57+00:00. Locator: List A, B and C management categories.