Invasive plants are a threat in many areas of Ontario, including here in the Kingston region. Tackling the issue begins with awareness, and in this week’s Ask a Master Gardener, Ruthie Cummings provides an introduction to wild parsnip identification, concerns and control strategies.

What are Invasive Species?

According to the Ontario Invasive Plant Council  they are “plants, animals, and micro-organisms that are found outside of their natural range, and whose presence poses a threat to environmental health, the economy, or society (Government of Canada, 2004)”. 

Wild Parsnip

Wild parsnip (Pastinaca sativa) is a member of the carrot family (Apiaceae) and was likely brought to North America by early settlers. As with so many other invasive species, it has enjoyed great success in the wild. It tends to be found in disturbed locations such as roadsides, fence rows and trails, and prefers full sun. It out-competes native vegetation, crowding out other lower-growing plants. 

Identification

Wild parsnip is a short lived perennial, characterized by:

  • Light green, hollow grooved stem
  • Thick taproot
  • Height up to 1.5 meters
  • Alternate leaves which are pinnately compound with 5-15 leaflets
  • Leaflets are oval or oblong, 5-10 cm long
  • Leaf edges are saw toothed 
  • Yellow flower clusters are compound umbels 10-20 cm across, flowering in June-Aug
  • After flowering, dry oval fruit (schizocarp) is produced, 5-7 mm long

Wild parsnip contains toxic compounds that will cause serious burns, rashes and blisters if skin is exposed to plant sap and then sunlight

Look-a-likes

Cow parsnip

Control

Depending on the size of the wild parsnip patch, it may be possible to remove them manually (if <100 plants), taking great care to avoid exposure. Plants should be dug out, including the taproot and placed in a black plastic bag in the sun for a week. It should not be burned or composted – local  municipalities can advise if bags may be landfilled. Avoid “weed whacking” as this spreads toxic sap over everything in the vicinity.  Large patches may need control by a professional.

Much more information on wild parsnip identification and control is available at:
Ontario Invasive Plant Council

Invasive Species Centre