Invasive Species and Noxious Weeds



An Invasive Species is any plant or animal species that is introduced into an environment where the species is not native. There are numerous examples of plants, insects, birds and animals that have been transplanted from their natural environments, either by accident or intentionally, into areas where they end up having a serious impact on the natural ecosystem. In some cases, climate change is contributing factor in some plant and animal species creating environmental damage as the plants and animals extend into new areas, or the natural controls against them collapse. The Pine Beetle is often noted as an example of how the warmer and shorter winters contributed to the massive infestations in BC.

In addition to the natural environment impacts, some invasive plants can speed up the deterioration of public and private infrastructure. Just as the tree that you planted 20 years ago in the back yard has now grown to the point that the root system is pushing up your driveway, or the Ivy you planted has completely grown over your retaining wall and rooted into the cracks in the concrete or wood ties, invasive plants can accelerate the destruction of man-made materials.


Information on Knotweed 

Variation Identification

The City of Prince Rupert is currently working with the Northwest Invasive Plant Council to deal with this noxious plant. There are four variations of knotweed - Himalayan, Giant Knotweed, Bohemian and Japanese. Knotweeds grow aggressively and are very hard to kill.  All knotweed species in BC can grow through concrete and asphalt, damaging infrastructure.  This can result in significant control, management and repair costs. This is why it is so important that knotweed is identified and treated in our community.

Below are images to help you identify the different varieties:

Bohemian Knotweed         Himalayan Knotweed        Japanese Knotweed           Giant Knotweed

  • These four species can grow larger than 2 m tall, with the giant knotweed being capable of reaching almost 5 m.
  • Leaves are mostly heart-to-triangular shaped in all species except for the Himalayan, which are elongated and tapered.
  • Giant knotweed leaves are twice as large as the other three species, which are 8 to 10 cm wide and 15 cm in length.
  • Leaf shape resembles a dogwood or lilac species, but their leaves grow opposite each other on woody stems.
  • All species bloom July to September, forming clusters of small flowers that are greenish-white, or pinkish white in Himalayan knotweed.
  • Stems are smooth, hollow and green coloured. They grow in dense thickets and remain standing as bare stalks in winter. The Himalayan knotweed’s stem is redder in colour than the other three.
  • The fruit of all four species are dark, smooth, and a few millimetres in size, however, the Himalayan knotweed is not winged.

Additional information is available below: 

Knotweed Information
Knot on my Property - Invasive Species Council website on Japanese Knotweed
How to Identify Knotweed


The City tracks the locations and varieties of knotweed in our community to the best of our ability, and coordinates treatment on City property. To report any instance of knotweed, on or off City property, see the reporting form below:

Knotweed Reporting Form

If you have positively identified Knotweed on your property and are looking for treatment options, you can contact Spectrum Resource Group, the main invasive plant contractor for the Skeena/Prince Rupert Region. Please call 1-306-730-5598 or email to coordinate treatment.

**PLEASE NOTE: Cow parsnip is NOT knotweed


Information on Cow Parsnip vs. Giant Hogweed

We know, they look the same! The primary difference between the two species (which are in the same family) is their size, leaf shape, and the general higher severity of burns/skin lesions that can accompany Giant Hogweed as compared to Cow Parsnip (though both can be nasty).

Cow Parsnip is a native species and therefore is not considered invasive, and the City does not treat it. However given the possibility of adverse reaction, please do not touch the plants or ensure you wear appropriate protection when handling it. Best practices for removing it from your property include:

1. Using appropriate protection (gloves, goggles, full length sleeves) when handling the plant;

2. Avoiding the use of lawnmowers and weedwhackers, which may spread the plants secretions and/or seeds;

3. Leaving the plants to dry out once cut back, then bagging them in black plastic bags before sending to the landfill or burning them;

4. Covering the exposed root system with material to block out the light, or treating with pesticide to stop it from spreading; and,

5. Avoiding composting any of the plant material, which may cause it to spread.

Please note that although Cow Parsnip is common here, Giant Hogweed has never been positively identified in Prince Rupert. If you believe that you have identified Giant Hogweed based on the above description, please report it to the Northwest Invasive Plant Council at: 1-888-933-3722 or through the Report a Weed application, available here: