Deceptively dangerous weed
Knowledge is power when it comes to dealing with noxious weeds such as wild parsnip.
Wild parsnip (Pastinaca sativa) is an invasive plant native to Europe and Asia. It was likely brought to North America by European settlers, who grew it for its edible root. Since its introduction, wild parsnip has escaped from cultivated gardens and spread across the continent.
Wild parsnip, which is also known as poison parsnip, is a member of the carrot/parsley family. It typically grows a low, spindly rosette of leaves in the first year while the root develops. In the second year it flowers on a tall stalk and then dies. The plant can form dense stands and spreads quickly in disturbed areas such as abandoned yards, waste dumps, meadows, open fields, roadsides and railway embankments. Its seeds are easily dispersed by wind and water, and on mowing or other equipment.
Like giant hogweed and other members of the carrot family, it produces sap containing chemicals that can cause human skin to react to sunlight, resulting in intense burns, rashes or blisters.
In North America, scattered wild parsnip populations are found from British Columbia to California, and from Ontario to Florida. It has been reported in all provinces and territories of Canada except Nunavut. The plant is currently found throughout eastern and southern Ontario, and researchers believe it is spreading from east to west across the province.
Flowers grow in yellowish-green clusters.
Impacts of wild parsnip
The plant can form dense stands that outcompete native plants, reducing biodiversity.
Stem, leaves, and flowers contain chemicals that can increase skin sensitivity to sunlight and cause severe dermatitis.
Wild parsnip reduces the quality and saleability of agricultural forage crops such as hay, oats, and alfalfa.
Chemical compounds in the plant are known to reduce weight gain and fertility in livestock that eat it.
How to identify wild parsnip
Growing up to 1.5 metres tall, the single green stem is two to five centimetres thick and smooth with few hairs.
Compound leaves are arranged in pairs, with sharply toothed leaflets that are shaped like a mitten.
Yellowish green flowers form umbrella-shaped clusters 10 to 20 centimetres across.
Seeds are flat and round.
What to do
If you have small clusters of wild parsnip on your property (fewer than 100 plants), you may be able to manage the plant yourself. Wear protective clothing and dispose of plants carefully, as described below. To remove larger infestations (thousands of plants), you will likely need a professional exterminator and repeated treatments over several years.
Wear protective clothing, including waterproof gloves, longsleeved shirts, pants and eye protection. A disposable spray suit over your normal clothing provides the best protection. Spray suits are commercial-grade waterproof coveralls. After working around the plant, remove your protective clothing carefully to avoid transferring any sap from your clothing onto your skin. Wash your rubber gloves with soap and water, then take off your spray suit or outer clothing. Wash your rubber gloves again and then take them off. Finally, take off your protective eye wear. Put nondisposable clothing in the laundry and wash yourself immediately with soap and water.
For a small infestation in a yard or garden (fewer than 100 plants), dig out as much of the taproot as you can with a sharp shovel or spade. Digging is most effective in the spring when the soil is moist and the taproot is more easily removed. Follow-up digging will be required every few weeks to deal with re-growth (if the taproot was not completely removed) or missed plants.
Another method of control is to cover the dug or mowed areas with black plastic to smother new growth of all plants.
HARDY NEMESIS: Poison parsnip, which can cause severe skin damage, continues to spread across rural areas.