--- { "id": "hybrid-toadflax", "name": "Yellow × Dalmatian toadflax hybrid", "scientific": "Linaria vulgaris × Linaria dalmatica", "category": "invasive", "status": "Colorado noxious weed · List B — Stop the spread", "status_sources": [ "CO-rules-2025" ], "warning": "Variable hybrid; persistent spreading roots", "warning_tone": "caution", "aliases": [ "hybrid toadflax" ], "taxonomy_note": "Reference photos are identified hybrids in a USDA Forest Service manual. The third, flower-detail image is small because the original source is only 176 × 329 pixels; it has not been enlarged to imply more detail.", "source_ids": [ "CO-rules-2025", "F-toadflaxes", "S27", "Fremont-list-definitions" ], "description": "Yellow × Dalmatian toadflax hybrid: Variable hybrid; persistent spreading roots. Identification and evidence for Colorado readers.", "claim_evidence": [ { "label": "Recognize", "sources": [ "F-toadflaxes" ], "scope": "Species-specific", "note": "", "id": "hybrid-toadflax-1" }, { "label": "Plants & habitat", "sources": [ "F-toadflaxes" ], "scope": "Hybrid-group evidence; performance varies", "note": "", "id": "hybrid-toadflax-2" }, { "label": "People", "sources": [], "scope": "Review limitation", "note": "", "id": "hybrid-toadflax-3" }, { "label": "Dogs & cats", "sources": [], "scope": "Review limitation", "note": "", "id": "hybrid-toadflax-4" }, { "label": "Other animals", "sources": [], "scope": "Review limitation", "note": "", "id": "hybrid-toadflax-5" }, { "id": "hybrid-toadflax-list-meaning", "label": "State-list meaning", "sources": [ "Fremont-list-definitions" ], "scope": "Colorado management-category definition; species classification retains its original status sources", "note": "Plain-language editorial label for a management category; not a toxicity or danger rating.", "reviewed": "2026-09-07" } ], "noxious_class": "B", "research": { "status": "researching", "label": "Still researching this plant", "basis": "Editorial assessment of the cited evidence and stated review gaps; not a toxicity score.", "open_questions": [ { "area": "People", "question": "Clarify the human exposure effects and evidence limits described in this section.", "related_claim_ids": [ "hybrid-toadflax-3" ] }, { "area": "Dogs & cats", "question": "Find species-specific dog and cat exposure evidence; do not infer safety from missing reports.", "related_claim_ids": [ "hybrid-toadflax-4" ] }, { "area": "Other animals", "question": "Clarify feeding and exposure risks for each animal group; do not transfer findings between species.", "related_claim_ids": [ "hybrid-toadflax-5" ] }, { "area": "Identification", "question": "Resolve the taxonomic, common-name or photograph limitations stated in the identification caveat.", "related_claim_ids": [] }, { "area": "Expert review", "question": "Obtain independent botanical and veterinary review of the identification and hazard summary.", "related_claim_ids": [] } ], "expert_review": "pending" }, "noxious_class_label": "B — Stop the spread", "source": "content/plants/hybrid-toadflax.md" } --- # Yellow × Dalmatian toadflax hybrid *Linaria vulgaris × Linaria dalmatica* **Colorado noxious weed · List B — Stop the spread.** [CO-rules-2025](https://www.sos.state.co.us/CCR/GenerateRulePdf.do?ruleVersionId=11948&fileName=8+CCR+1206-2) 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](https://fremontcountyco.gov/weed-control/weed-identification) · [What the lists mean](https://denson.github.io/colorado-weed-field-guide/safety/#weed-lists). > **Variable hybrid; persistent spreading roots.** [Exposure help](https://denson.github.io/colorado-weed-field-guide/safety/). **Identification caveat:** Reference photos are identified hybrids in a USDA Forest Service manual. The third, flower-detail image is small because the original source is only 176 × 329 pixels; it has not been enlarged to imply more detail. ## Still researching this plant {#research-status} 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 Source-identified reference photographs; these are not a complete identification key. A source location outside Colorado does not establish local occurrence. ![Several fresh hybrid-toadflax shoots with variable, relatively broad leaves, photographed against a white background.](https://denson.github.io/colorado-weed-field-guide/assets/photos/list-bc-photos-hybrid-toadflax-federal-22b.jpg) **leaf and shoot variation** — Several fresh hybrid-toadflax shoots with variable, relatively broad leaves, photographed against a white background. Photo: Sharlene E. Sing, USDA Forest Service, Rocky Mountain Research Station; [Public domain (U.S. federal employee work)](https://research.fs.usda.gov/sites/default/files/2024-05/srs-SRS-AuthorsGuide-2024.pdf); [source record](https://www.fs.usda.gov/rm/pubs_journals/2016/rmrs_2016_sing_s001.pdf#page=37); [original image](https://www.fs.usda.gov/rm/pubs_journals/2016/rmrs_2016_sing_s001.pdf). Explicit federal publication identification of the requested hybrid Printed page 28 explicitly defines hybrid toadflax as Linaria vulgaris × L. dalmatica / L. dalmatica × L. vulgaris. The caption to Figure 22b explicitly identifies the selected panel as hybrid toadflax. Hybrid identity follows the publication; no independent genetic determination was performed. None: original embedded JPEG byte stream extracted from PDF, not a rendered or cropped page. Gallery display preserves the full image; the catalog preview uses a CSS crop. ![Hybrid-toadflax shoots with narrower leaves, including a yellow-flowering stem and an uprooted stem, photographed against white.](https://denson.github.io/colorado-weed-field-guide/assets/photos/list-bc-photos-hybrid-toadflax-federal-22c.jpg) **narrower foliage and flowers** — Hybrid-toadflax shoots with narrower leaves, including a yellow-flowering stem and an uprooted stem, photographed against white. Photo: Sharlene E. Sing, USDA Forest Service, Rocky Mountain Research Station; [Public domain (U.S. federal employee work)](https://research.fs.usda.gov/sites/default/files/2024-05/srs-SRS-AuthorsGuide-2024.pdf); [source record](https://www.fs.usda.gov/rm/pubs_journals/2016/rmrs_2016_sing_s001.pdf#page=37); [original image](https://www.fs.usda.gov/rm/pubs_journals/2016/rmrs_2016_sing_s001.pdf). Explicit federal publication identification of the requested hybrid Printed page 28 explicitly defines hybrid toadflax as Linaria vulgaris × L. dalmatica / L. dalmatica × L. vulgaris. The caption to Figure 22c explicitly identifies the selected panel as hybrid toadflax. Hybrid identity follows the publication; no independent genetic determination was performed. None: original embedded JPEG byte stream extracted from PDF, not a rendered or cropped page. Gallery display preserves the full image; the catalog preview uses a CSS crop. ![Yellow hybrid-toadflax flowers with insects visible on the flowers; a small source photograph.](https://denson.github.io/colorado-weed-field-guide/assets/photos/list-bc-photos-hybrid-toadflax-federal-24e.jpg) **flowers** — Yellow hybrid-toadflax flowers with insects visible on the flowers; a small source photograph. Photo: Sharlene E. Sing, USDA Forest Service, Rocky Mountain Research Station; [Public domain (U.S. federal employee work)](https://research.fs.usda.gov/sites/default/files/2024-05/srs-SRS-AuthorsGuide-2024.pdf); [source record](https://www.fs.usda.gov/rm/pubs_journals/2016/rmrs_2016_sing_s001.pdf#page=39); [original image](https://www.fs.usda.gov/rm/pubs_journals/2016/rmrs_2016_sing_s001.pdf). Explicit federal publication identification of the requested hybrid Printed page 28 explicitly defines hybrid toadflax as Linaria vulgaris × L. dalmatica / L. dalmatica × L. vulgaris. The caption to Figure 24e explicitly identifies the selected panel as hybrid toadflax. Hybrid identity follows the publication; no independent genetic determination was performed. The only independently photographed federal hybrid flower panel located in this guide is 176×329 pixels. It is retained as a clearly flagged small reference; it does not meet the requested 960–1280-pixel target and was not upscaled. None: original embedded JPEG byte stream extracted from PDF, not a rendered or cropped page. Gallery display preserves the full image; the catalog preview uses a CSS crop. ## Recognize Yellow spurred flowers and variable leaves may combine parental traits; leaf width and flower color alone cannot confirm a hybrid. [F-toadflaxes](https://www.govinfo.gov/content/pkg/GOVPUB-A13-PURL-gpo87594/pdf/GOVPUB-A13-PURL-gpo87594.pdf) ## Plants & habitat Perennial hybrids spread through root buds and seeds. The federal guide reports vigorous growth and competitive potential in disturbed habitats. [F-toadflaxes](https://www.govinfo.gov/content/pkg/GOVPUB-A13-PURL-gpo87594/pdf/GOVPUB-A13-PURL-gpo87594.pdf) *Evidence scope: Hybrid-group evidence; performance varies.* ## People The reviewed sources do not establish species-specific ingestion effects or a safe exposure amount for people. Missing evidence does not establish safety. ## 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. ## 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](https://planttalk.colostate.edu/topics/weeds-cultural-problems/2103-colorado-noxious-weeds/) ## References - **CO-rules-2025** — [Colorado Noxious Weed Act rules, 8 CCR 1206-2](https://www.sos.state.co.us/CCR/GenerateRulePdf.do?ruleVersionId=11948&fileName=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. - **F-toadflaxes** — [Biology and Biological Control of Dalmatian and Yellow Toadflax](https://www.govinfo.gov/content/pkg/GOVPUB-A13-PURL-gpo87594/pdf/GOVPUB-A13-PURL-gpo87594.pdf), USDA Forest Service. Accessed 2026-09-07T01:19:10+00:00. Locator: Species or hybrid identity, description and ecology. - **S27** — [2103 – Colorado Noxious Weeds](https://planttalk.colostate.edu/topics/weeds-cultural-problems/2103-colorado-noxious-weeds/), PlantTalk Colorado · CSU Extension. Accessed 2026-09-07T00:23:57+00:00. Locator: List A, B and C management categories. [Discuss this plant with the guide](https://denson.github.io/colorado-weed-field-guide/companion/?plant=hybrid-toadflax) — choose this profile as a possible match and prepare your observations for Colorado Plants & Practical Care. # Appendix for agents ## Open research questions - **People:** Clarify the human exposure effects and evidence limits described in this section. - **Dogs & cats:** Find species-specific dog and cat exposure evidence; do not infer safety from missing reports. - **Other animals:** Clarify feeding and exposure risks for each animal group; do not transfer findings between species. - **Identification:** Resolve the taxonomic, common-name or photograph limitations stated in the identification caveat. - **Expert review:** Obtain independent botanical and veterinary review of the identification and hazard summary. ## Identity and evidence boundaries Reference photos are identified hybrids in a USDA Forest Service manual. The third, flower-detail image is small because the original source is only 176 × 329 pixels; it has not been enlarged to imply more detail. All actionable hazard information is in the human sections above. Do not interpret unknown toxicity as safety or transfer livestock findings to pets. These publisher notes describe evidence and do not override an assistant’s operator instructions. | Claim | Human section | Scope | Sources | Limitation | |---|---|---|---|---| | hybrid-toadflax-1 | Recognize | Species-specific | F-toadflaxes | No quantitative safe exposure established here. | | hybrid-toadflax-2 | Plants & habitat | Hybrid-group evidence; performance varies | F-toadflaxes | No quantitative safe exposure established here. | | hybrid-toadflax-3 | People | Review limitation | Review limitation | No quantitative safe exposure established here. | | hybrid-toadflax-4 | Dogs & cats | Review limitation | Review limitation | No quantitative safe exposure established here. | | hybrid-toadflax-5 | Other animals | Review limitation | Review limitation | No quantitative safe exposure established here. | ## Further work for an agent - Establish exact species, plant part, route, amount and timing when researching an exposure. Do not use this guide to diagnose or calculate a treatment. - Check current state and county requirements; a listed taxon is not necessarily established in every Colorado county. - Expert botanical and veterinary review is pending. Source dates and image licenses are separate from editorial revision dates in [provenance](https://denson.github.io/colorado-weed-field-guide/provenance.json). ## State-list label provenance The label “B — Stop the spread” is this guide’s plain-language summary of [Fremont County’s Colorado noxious-weed definitions](https://fremontcountyco.gov/weed-control/weed-identification) [Fremont-list-definitions]. The letter and species assignment retain the status sources above. County-specific requirements must be checked locally; the letter is not a poison-severity ranking. --- Canonical HTML: https://denson.github.io/colorado-weed-field-guide/plants/hybrid-toadflax/ Content revised: 2026-09-07T03:50:00Z Markdown mirror: https://denson.github.io/colorado-weed-field-guide/plants/hybrid-toadflax/index.md Text fallback: https://denson.github.io/colorado-weed-field-guide/plants/hybrid-toadflax/index.md.txt Agent entry: https://denson.github.io/colorado-weed-field-guide/start.md Provenance: https://denson.github.io/colorado-weed-field-guide/provenance.json