Colorado Plants & Practical Care

Biggest concerns

Start with the kind of problem you need to prevent. These are selected routes into the guide, not a universal severity ranking. Read each profile for the affected animal group and evidence limits. For suspected exposure, use the safety guide.

State-list labels describe management requirements, separately from these hazards. What Lists A, B and C mean.

Serious ingestion hazards

Plants with serious poisoning warnings. Affected species and evidence strength differ; use the individual profile before drawing conclusions about a person or animal.

Apocynum cannabinum: A dense leafy flowering stand beside a cultivated field.

Hemp dogbane

Apocynum cannabinum

Cardiac-glycoside poisoning hazard for people and animals

Photo: Ayotte, Gilles, 1948- · CC BY-SA 4.0 · Credits and sources

Pets, paws and skin contact

A route to awns, burs, sharp points and irritating plant contact, including poison-ivy oil carried on fur.

Pasture, hay and livestock losses

For landowners and animal keepers: forage poisoning and injury deserve their own review. Livestock findings are not pet exposure limits.

Dry grass, tumbleweeds and fire concerns

Read the profiles for the evidence about dry vegetation, tumbling plants and effects on land management.

Persistent roots and habitat displacement

Plants whose spread or persistence can make restoration and routine garden management difficult. Methods depend on the site and confirmed identity.

Erigeron canadensis: A tall upright stem topped by a broad, finely branched pale mature head cluster.

Horseweed

Erigeron canadensis

Fast windborne spread; some populations resist herbicides

Photo: Enrico Blasutto · CC BY-SA 3.0 · Credits and sources

Waterways and aquatic habitats

Use the individual accounts to understand spread and identification before moving plants, water or equipment from an affected site.

Pollen and seasonal allergies

Ragweed profiles separate documented allergy concerns from species-specific questions still under research. This is not a local pollen forecast.

Early detection matters

All List A — Eradicate entries are included in the coverage checklist. Statewide eradication requirements make these reporting priorities even where a plant is not yet widespread. CO-rules-2025.

Content revised · Source checks dated separately in the references.

Read with an AI assistant · Markdown and sources

Markdown: https://denson.github.io/colorado-weed-field-guide/biggest-concerns/index.md
Text fallback: https://denson.github.io/colorado-weed-field-guide/biggest-concerns/index.md.txt
Start here: https://denson.github.io/colorado-weed-field-guide/start.md
Source ledger: https://denson.github.io/colorado-weed-field-guide/provenance.json