Noxious Plant Field Identification Checklist— free, no sign-up Download PDF
HSE ADVISOR CANADA
Noxious Plant Field Identification Checklist
A field reference for outdoor crews covering the five plants most likely to put a Canadian worker in hospital. Identification features, what each one actually does to skin, and the immediate response that changes the outcome — plus a pre-season briefing record for your hazard assessment.
How to use it. Print it, and keep a copy in each vehicle. Brief the crew before the season starts rather than after the first burn, and record the briefing in Part 2 so it lands in your hazard assessment file. To print: Click "Print" below → select Portrait orientation → enable Background graphics in print settings → Print. To fill in: Print and complete by hand, or use your browser's "Save as PDF" and fill the fields in any PDF editor.
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Noxious Plant Field Card
Identification and immediate response · Canadian outdoor crews
HSE ADVISOR CANADA hseadvisor.ca
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Season / year:
The two mechanisms that matter
Mechanism
What happens
Why the response differs
Phototoxic (sap + sunlight)
Sap chemicals react with UV light and burn the skin. Not an allergy — anyone exposed reacts.
Getting out of sunlight matters as much as washing. Cover the skin immediately.
Allergic contact dermatitis
An oil triggers an immune reaction. Severity varies between people and builds with exposure.
Wash off the oil fast, and decontaminate clothing and tools that carry it.
Mechanical
Physical needles or spines inject irritants on contact.
Usually short-lived. Matters most because a startled worker may fall or drop a tool.
1. Giant hogweed — the most dangerous
Feature
What to look for
Height
Up to five metres — far taller than anything around it.
Stem
Hollow, thick, with coarse bristles and purple blotches.
Flowers
Large white clusters, umbrella-shaped, can reach 80 cm across.
Where
Roadsides, waterways, disturbed land. Documented in Ontario, BC, Quebec and the Atlantic provinces.
Harm
Phototoxic. Sap plus sunlight causes blistering that can reach third-degree burn severity. Reaction can begin within 15 minutes of sun exposure and peaks 48–72 hours later. Scarring can be permanent. Sap in the eyes can cause temporary or permanent blindness.
This is not an allergic reaction. Anyone who gets the sap on their skin and then steps into sunlight will burn. There is no such thing as not being sensitive to it.
2. Wild parsnip — the one crews miss most
Feature
What to look for
Height
Smaller than giant hogweed, typically waist to chest height.
Flowers
Flat-topped yellow clusters — the quickest way to tell it from hogweed.
Stem
Hollow, grooved, green.
Where
Roadside ditches and unmaintained right-of-ways. Now found in every province, and abundant along Ontario’s 400-series corridors and rural right-of-ways.
Harm
Same phototoxic mechanism as giant hogweed. Responsible for more documented workplace injuries in eastern Canada simply because it is far more common. Mowing an infested area without PPE has produced burns across an entire crew.
3. Poison ivy
Feature
What to look for
Leaves
Three leaflets on each stalk. Glossy in spring, red in autumn.
Form
Ground cover, shrub or climbing vine.
Where
Fence lines, disturbed soil, forest margins. Every province except Newfoundland and Labrador.
Harm
Urushiol oil causes allergic contact dermatitis. Present in every part of the plant year-round, including dead vines in winter. Rash typically peaks 24–72 hours after contact and spreads via contaminated clothing, gloves and tools.
4. Stinging nettle and 5. Cow parsnip
Plant
Identification
Harm
Stinging nettle
Toothed leaves with fine hairs on leaves and stems. Moist, disturbed ground across the country.
Hollow silica needles inject formic acid and histamine. Immediate pain, generally short-lived. Main risk is a startled worker falling or dropping a tool.
Cow parsnip
Native, smaller than giant hogweed, white flower clusters. Common in BC and Alberta.
Same phototoxic mechanism, less potent. Treat as hogweed until identified with confidence.
Identification errors go both ways. Workers unfamiliar with giant hogweed sometimes dismiss it as cow parsnip — and sometimes report cow parsnip as hogweed. If the crew cannot tell them apart with confidence, treat every tall white-flowered umbellifer as giant hogweed.
If a worker is exposed — phototoxic sap
Cover the skin from sunlight immediately — clothing, a towel, anything opaque. Do this first.
Wash the area thoroughly with soap and water. Do not rub the skin.
Get out of the sun and stay out of the sun for at least 48 hours, even if nothing is visible yet.
If sap contacted the eyes, flush with clean water immediately and seek medical attention.
See a physician as soon as possible — corticosteroids prescribed early can reduce blistering severity.
Record it as a workplace incident and review the hazard assessment.
No visible reaction does not mean no exposure. The burn develops after UV exposure, not on contact. A worker who feels fine at noon can blister badly by the following evening.
If a worker is exposed — urushiol (poison ivy)
Wash skin with soap and cool water as soon as possible — speed matters more than technique.
Wash all clothing, gloves, boots and tools separately. The oil transfers and re-exposes.
Do not burn cut vegetation. Inhaling smoke containing urushiol can cause serious respiratory injury.
Seek medical attention for widespread rash, facial involvement, or any breathing difficulty.
Controls before the season
Requirement
What good looks like
Y / N / N-A
Evidence or gap
Plants in the hazard assessment
Noxious plants named as a hazard for the areas your crews work.
Pre-season crew briefing
Delivered before the growing season, with identification photos.
PPE specified
Impermeable gloves, long sleeves, eye protection for mowing or brushing infested areas.
Wash facilities available
Soap and water accessible on site or in vehicles.
Known infestations mapped
Locations recorded and flagged for crews before they arrive.
Mowing controls
Procedure for mowing or trimming infested ground, including downwind and spray considerations.
Noxious Plant Field Identification Checklist · HSE Advisor Canada · Free to use and adapt.
Identification guidance only. When in doubt, do not touch the plant. Seek medical attention for any suspected exposure, and confirm control obligations against the weed control legislation in your province.