Local Governments Join Forces to Bust Invasive Plants

July 13, 2017

Local governments in the Comox Valley have once again joined forces to bust invasive knotweed and Giant hogweed. Both plants are considered alien invasive species in BC and if left unchecked can wreak havoc on our local ecosystems and diminish property values. And in the case of giant hogweed, can lead to third degree burns when in contact with skin, due to its clear phototoxic sap.

This successful regional “Knot On My Property” program, first launched in 2013, includes all four local governments, the Town of Comox, City of Courtenay, Village of Cumberland and the Comox Valley Regional District (CVRD), and in partnership with the Coastal Invasive Species Committee (Coastal ISC). The goals of the program are to verify all knotweed and giant hogweed reports within these jurisdictions to provide to professionals to conduct treatments on select sites.

The 2016 program targeted 74 knotweed sites and 15 giant hogweed sites eradicating 10 completely and significantly reduced infested areas. These sites are now recorded in the provincial invasive alien plant program database for tracking and follow-up monitoring and treatment. Effective control usually takes three to five years.



Knotweed is considered one of the world's worst invaders. It is a hollow stem shrub, native to Asia that resembles bamboo. It can grow up to 4 centimetres a day and causes serious damage to foundations, driveways, and septic system, as well as natural habitats. In the UK, Japanese knotweed has spread rampantly and now homeowners cannot secure mortgages or insurance on properties with knotweed. Cutting, mowing, and pulling can stimulate shoot growth and may cause roots to spread further, resulting in new infestations up to 20 metres away. As well, knotweed has the ability to regenerate from a very small root or stem fragment and can remain dormant for many years.


Giant Hogweed

WARNING: Stem hairs and leaves contain a clear, highly toxic sap that, when in contact with the skin, can cause burns, blisters and scarring. Notes: WorkSafe BC has issued a Toxic Plant Warning for Giant hogweed.

Giant hogweed is an herbaceous perennial. Stems are hollow, ridged, and green with purple spots and may have stiff hairs present. When in flower, plants can grow to 6 metres tall. Flowers are small, white and clustered in large umbrella shaped heads and leaves are green and deeply incised (almost to leaf vein) and have three segments. Leaves can exceed 2.5 metres in length.



Local residents in CVRD's electoral areas can benefit from subsidized treatments by select spot application this summer, while treatments in Comox, Courtenay and Cumberland previously focused only on public lands they now offer treatments on both public and private lands as of 2017.

Coastal ISC appreciates the cooperation of all residents in addressing knotweed and giant hogweed. Reporting knotweed and giant hogweed is very important in controlling these priority invasive plants in the region. The Coastal Invasive Species Committee is asking the public to report sightings of knotweed and Giant Hogweed until the end of July by email info@coastalisc.com or calling 250-871-5117 in the Comox Valley; toll free on Vancouver Island 1-844-298-2532.

"Knotweed is known for causing a huge headache across British Columbia, but with the public's help we can prevent it from taking over our coastal communities. It's an invasive and aggressive plant that spreads easily and can impact property values, the environment, and can cause safety issues on roadways. This regional program will save considerable taxpayer dollars. Visit Knotonmyproperty.com, or pick up a booklet from your local government to learn how to defend your property from invasion" explains Don Hare, Executive Director of the Coastal ISC.

"The spread of knotweed has negative ecological and economic impacts and Giant Hogweed has serious health impacts. We are pleased to work with our local government’s region wide to combat invasive species in our area," said Edwin Grieve, chair of the Comox Valley Regional District electoral area services committee.

"Once again we're very pleased to be working in partnership with other local governments and our residents to help fight invasive species in our community. It's truly a collective effort. Taking these steps now is vital to protecting our natural ecosystems for future generations," added Mayor of Courtenay, Larry Jangula.

A knotweed and giant hogweed alert sheet, providing information on identification, proper disposal, and reporting options has been developed and is available on the CVRD website at www.comoxvalleyrd.ca/invasiveplants.

For more information on identification, common lookalikes of these plants and its damaging impacts, as well as other invasive species that are being managed in your area please visit the Coastal ISC website at www.coastalisc.com and click on the "Invasive Species" tab.