Weeds, are they noxious or a nuisance?

The issue of controlling invasive plants...or noxious bubbling to the surface once again

The issue of controlling invasive plants…or noxious weeds…is bubbling to the surface once again.

With the season winding down, ripe seeds are ready to spread further afield to ensure growth next season.

Invasive is a term that typically refers to non-native and exotic species, both plant and animal, which have an adverse environmental and economical affect on local habitat. Imported plants so named are deemed to have a detrimental impact on native habitat.

Many governments, such as our provincial government, have created two classifications to better distinguish between these problem plants — nuisance weeds and noxious weeds.

Noxious weeds refers to introduced species into a region that does not contain the insect predators or pathogens needed to keep them under control. These plant species destroy habitat; their aggressive growth habit overpowers the native species.

Through legislation, our province has a BC Weed Control Act that puts the onus on land owners to control the designated noxious plant species listed in the regulations. The list includes: Canada thistle (Cirsium arvense), gorse (Ulex europaeus) and yellow toadflax (Linaria vulgaris) to name but a few.

Some species are listed as noxious by the regional district only…such as wild mustard (Sinapsis arvensis) in the Peace River area. All of the noxious plants in this list are also regulated by the BC Weed Control Act.

Conversely, nuisance weeds refers to those species that have not made it onto any Weed Act list but are considered a nuisance by their more aggressive behaviour over the native species.

Surprisingly, this is where you will find field bindweed (Convolvulus arvensis) listed…as well as Scotch broom (Cytissus scoparius) and field horsetail (Equisetum arvense).

Giant hogweed (Heracleum mantegazzianum) and Japanese knotweed (Polygonum cuspidatum) were both listed as nuisance weeds a decade ago but have since been upgraded to the noxious list and are now regulated by the BC Weed Control Act.

As of Aug. 8, 2011, there were 39 plants on the noxious weeds list in all regions of B.C. This is up from a previous list of 21 species that was published in 2002.

Also on the 2011 list were a further 47 plants labelled as noxious weeds but only in certain regions of B.C. … not throughout. This number is up from the 28 species noted on the previous list.

By provincial law, we are not allowed to buy, sell or propagate those species that are listed in the BC Weed Control Act. Federally, we are regulated by the Seeds Act and Plant Protection Act.

According to the Seeds Act, there is an “allowable limit of weed seed content”…which, by my interpretation, means it is OK to have a certain amount of weed seed mixed in with lettuce seeds. The Plant Protection Act regulates the importation of a “few parasitic plants.”

Sounds ominous.

However, neither one of these federally-regulated Acts controls the importation of plant species for garden or landscape use that may potentially be aggressive plants in our country. This is mainly due to the fact that what is aggressive in Ontario, for instance, is not necessarily aggressive in B.C.

Hence the provincial regulations. And they vary.

For instance, Manitoba has a total of 500 plant species on their combined noxious and nuisance weeds lists. Wow! But I was surprised to see milkweed on the list…a food plant for Monarch butterflies. Are they kidding?

Our local regional district is currently updating their noxious weed bylaw to include a total of 21 plants.

It is high time we all become responsible gardeners and land stewards, ensuring no more plant seeds on the list are released into the environment. We should be actively working on eradicating the noxious weeds in our own neighbourhoods.

For more information on the BC Weed Control Act, visit

• • •

And speaking of websites, the Duchess of Dirt has one of her own now! Please check me out at and let me know what you think.

Leslie Cox co-owns Growing Concern Cottage Garden in Black Creek. Her column appears every second Friday.

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