A noxious weed is a plant that has been listed in the Schedule of Noxious Weeds found in Regulation 1096 made under the Weed Control Act.

In general, a species designated as a noxious weed under the Weed Control Act is one that:

  • is difficult to manage on agricultural land once established and will reduce the yield and quality of the crop being grown
  • negatively affects the health and well-being of livestock
  • poses a risk to the health and well-being of agricultural workers

Purpose of the Weed Control Act

The intent of the Weed Control Act is to reduce:

  • the infestation of noxious weeds that negatively impact on agriculture and horticulture lands
  • plant diseases by eliminating plant disease hosts such as common barberry and European buckthorn
  • health hazards to livestock and agricultural workers caused by poisonous plants

Noxious weed list

This list is commonly referred to as the "noxious weed list."

In Ontario, the following 25 weeds are designated as noxious under the Weed Control Act:

Common NameScientific Name
Barberry, commonBerberis vulgaris L.
Bedstraw, smoothGalium mollugo L.
Buckthorn, EuropeanRhamnus cathartica L.
Chervil, wildAnthriscus sylvestris (L.) Hoffmann
ColtsfootTussilago farfara L.
Crupina, commonCrupina vulgaris Cass.
Cupgrass, woollyEriochloa villosa (Thunb.) Kunth
Dodder spp.Cuscuta spp.
Dog-strangling vineVincetoxicum rossicum (Kleopow) Barbar.
Dog-strangling vine, blackVincetoxicum nigrum (L.) Moench
Goatgrass, jointedAegilops cylindrica Host
Hogweed, giantHeracleum mantegazzianum Sommier & Levier
Knapweed spp.Centaurea spp.
KudzuPueraria montana (Lour.) Merr.
Parsnip, wildPastinaca sativa L.
Poison-hemlockConium maculatum L.
Poison-ivyToxicodendron radicans (L.) Kuntze
Ragweed spp.Ambrosia spp.
Ragwort, tansySenecio jacobaea L.
Sow-thistle spp.Sonchus spp.
Spurge, cypressEuphorbia cyparissias L.
Spurge, leafyEuphorbia esula L.
Thistle, bullCirsium vulgare (Savi) Tenore
Thistle, CanadaCirsium arvense (L.) Scopoli
Tussock, serratedNassella trichotoma Hackel ex Arech.

Local weed by-laws

A municipal council may, subject to the approval of the minister, designate additional plants as local weeds through a by-law. The by-law must be made in accordance with section 10 of the Weed Control Act.

These local weeds are deemed to be noxious weeds in the area where the by-law applies.

Noxious weeds on your property

You must destroy a noxious weed if:

  • you are in possession of one of the weeds on the Schedule of Noxious Weeds
  • it is negatively impacting agriculture and horticulture lands

If you feel that your agricultural or horticultural land is being negatively impacted by noxious weeds, contact your local Weed Inspector.

How to destroy noxious weeds

You can destroy noxious weeds by:

  • pulling or removing the plants from the soil
  • cutting the roots or stalks of the plants before the seeds have developed sufficiently to ripen after the cutting
  • plowing or cultivating the soil in which the plants are growing
  • treating with an herbicide that causes the plants to be destroyed or prevents the growth of the plants or the ripening of their seeds

Contact your local Weed Inspector

Find the Weed Inspector in your area by contacting either: