Wild Parsnip Control in Ontario

What Is Wild Parsnip?

Wild parsnip is a biennial or short-lived perennial in the carrot family, typically growing between one and one and a half metres tall when flowering. It produces flat-topped clusters of small yellow flowers, which distinguishes it from the many white-flowered relatives found along Ontario roadsides.

In its first year it forms a low rosette of compound leaves and is easily overlooked. It flowers and sets seed in a later season, then dies, so a population is sustained by the seed it produces.

Why Is Wild Parsnip a Problem?

Like giant hogweed, wild parsnip sap can make skin highly sensitive to sunlight, causing burns and blistering after exposure. This matters most in the places it grows: roadsides, trail edges, ditches and field margins where road crews, cyclists, walkers, farm workers and children come into contact with it.

It also spreads aggressively along corridors and can dominate roadside and field-edge vegetation, and it colonises hay fields and pasture where it affects land use.

• Sap can cause burns and blistering after sun exposure
• Grows in high-contact locations: roadsides, trails, ditches and field edges
• Presents a hazard to road maintenance crews and the public
• Spreads rapidly along transportation corridors
• Colonises hay fields, pasture and unmanaged open ground

Where Does It Commonly Grow?

Wild parsnip is strongly associated with road corridors. Ditches, shoulders and road allowances provide disturbed, open, sunny conditions and continuous connectivity, and mowing equipment moving along a corridor distributes seed efficiently if timed poorly.

It is also common in old fields, pastures, trail edges, utility corridors and other regularly disturbed open ground.

How Is Wild Parsnip Managed?

Because wild parsnip depends on seed, management focuses on preventing seed production and depleting the existing seed bank. A program that reduces flowering plants each season progressively shrinks the population.

Where herbicide treatment is appropriate, it is generally most effective on rosettes rather than on mature flowering plants. Mowing can contribute when it is timed to prevent seed set, but poorly timed mowing spreads mature seed along the corridor and can make the situation worse.

Corridor programs also consider sequencing so that equipment does not carry seed from infested sections into clean ones.

Managing Contact Risk on Public Corridors

Where wild parsnip grows along publicly accessible roadsides and trails, contact risk is a practical management driver in addition to the vegetation objective. Programs typically prioritise high-contact locations such as intersections, trail heads, laybys and areas adjacent to residential property.

Crews working in infested corridors require appropriate protective equipment and awareness of the hazard.

Wild Parsnip Control in Northeastern and Central Ontario

Invasive Veg Solutions Inc. provides roadside and property vegetation management throughout Northeastern and Central Ontario, including municipal road allowances, transportation corridors, rights-of-way and private land.

Wild parsnip is among the species most frequently encountered on road corridors in this territory. Whether a corridor is best served by treatment, timed mechanical work or a combination is determined by survey and assessment.