Prickly lettuce
Discuss this plant with the guide — choose this profile as a possible match and prepare your observations for Colorado Plants & Practical Care.
Lactuca serriola
Common introduced weed · not on state Lists A/B/C. C-floristic-2020 CO-rules-2025
Prickly leaves and prolific windborne seed. Exposure help.
Identification caveat: Wild lettuce names refer to several species. Lactuca serriola is not a substitute for cultivated lettuce or a verified medicinal product.
Still researching this plant
This is a sourced working profile. Evidence is incomplete for 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
Source-identified reference photographs; these are not a complete identification key. A source location outside Colorado does not establish local occurrence.
Teun Spaans (TeunSpaans) · Public domain
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. Source-identified L. serriola. Leaf lobing varies, and related wild lettuces may share a prickly midrib; the photograph is a reference, not a determination of an unknown specimen.
Wikimedia server-resized derivative, reduced from the original; no crop, color change, upscaling, or generative editing. Gallery display preserves the full image; catalog preview may use a CSS crop.
Teun Spaans (TeunSpaans) · Public domain
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. Source-identified L. serriola. Leaf lobing varies, and related wild lettuces may share a prickly midrib; the photograph is a reference, not a determination of an unknown specimen.
Wikimedia server-resized derivative, reduced from the original; no crop, color change, upscaling, or generative editing. Gallery display preserves the full image; catalog preview may use a CSS crop.
Teun Spaans (TeunSpaans) · Public domain
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. Source-identified L. serriola. Leaf lobing varies, and related wild lettuces may share a prickly midrib; the photograph is a reference, not a determination of an unknown specimen.
Wikimedia server-resized derivative, reduced from the original; no crop, color change, upscaling, or generative editing. Gallery display preserves the full image; catalog preview may use a CSS crop.
Identification
An upright annual or biennial with milky sap, spines along the underside of the leaf midrib and small yellow flower heads. Leaves may stand nearly vertical. C-descriptions
People
Leaf spines are a handling concern. No ingestion safety is established by this profile. C-descriptions
Evidence scope: Handling precaution inferred from leaf structure.
Dogs & cats
The reviewed sources do not establish species-specific ingestion effects or a safe exposure amount for dogs or cats. Missing evidence does not establish safety.
Other animals
The reviewed sources do not establish species-specific ingestion effects or a safe exposure amount for livestock. Missing evidence does not establish safety.
Plants & habitat
It invades disturbed garden soils. C-descriptions
Management & timing
Pull young plants from moist soil before flowers mature. C-descriptions
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
- C-floristic-2020 — Colorado Floristic Quality Assessment: 2020 Update, Colorado Natural Heritage Program, Colorado State University. Accessed 2026-09-07T02:27:33+00:00. Locator: Appendix B, Colorado species list: scientific name and native/non-native fields.
- 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.
- C-descriptions — Weed descriptions, Colorado State University Extension. Accessed 2026-09-07T00:24:02+00:00. Locator: Species entries.
- 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.