Invasive Plants

Invasive plants, also called exotics, noxious weeds, or alien species, are imported from other parts of the world and can cause ecological destruction. These alien invaders arrive without their natural controls, such as insects, diseases, and competing plants, to keep them in check, and as a result may spread rapidly, crowding or choking out the existing native plants.

Invasive plants are spread through illegal dumping of garden waste, movement of soil and seed dispersal by wildlife, wind and water. To help prevent and control the spread of invasive plant species and protect the ecological integrity of our parks, the City has developed an Invasive Plant Management Strategy.

Strategy Goals

The City’s Invasive Plant Management Strategy, adopted by Council in 2013, guides the management of invasive plants on public lands and facilitates the management of invasive plants on private lands. The purpose of the Invasive Plant Management Strategy (Strategy) is to provide the City with an efficient, cost effective, coordinated approach to managing invasive plants.

The goals of the Invasive Plant Management Strategy are to have an effective, adaptable strategy that will:

  1. Outreach and Education: Increase awareness & knowledge of invasive plants within the community;
  2. Control Implementation: Measurably reduce invasive plant density & distribution;

  3. Stakeholder Coordination: Coordinate efforts between all stakeholders & resources;

  4. Assessment and Restoration: Effectively monitor, maintain & restore the City’s parks and natural areas; and

  5. Policy and Adaptive Management: Develop effective policy and practice adaptive management.

If left unchecked, invasive plant species will continue to spread and further degrade the environment, cause detrimental economic impacts and pose human health risks. By implementing the actions identified in the Strategy the City is anticipated to achieve the goals and thus ensure safe, sustainable, and ecologically healthy areas for the benefit of future generations.

Top Priority Species

Noxious weeds are invasive species recognized by the BC government as highly destructive, competitive, and difficult to control. Like other invasive species, they are non-native plants that have been introduced to BC without the predators that help keep them in check in their native habitats. The BC Weed Control Act imposes a duty on all land owners to control designated noxious weeds. As such, the City is required under the BC Weed Control Act to control these species.

In 2011, eighteen species were added as provincially noxious under the B.C. Weed Control Act, including the following species significant to the City:

  • Giant hogweed (Heracleum mantegazzianum)
  • Knotweed, Bohemian (Fallopia bohemica)
  • Knotweed, Giant (Fallopia sachalinensis)
  • Knotweed, Himalayan (Polygonum polystachyum)
  • Knotweed, Japanese (Fallopia japonica)

Due to this designation, combined with the results of the Invasive Inventory, Giant Hogweed and knotweed species have been identified as the City's highest priority species. These species pose public health risks, present slope stability concerns, and can damage buildings and infrastructure.

 

Giant Hogweed

Giant HogweedWARNING: The stem and stem hairs of the Giant Hogweed exude a clear watery sap, which sensitizes the skin to ultraviolet radiation. Exposure to this sap can result in severe burns and blistering to the affected areas. If you are exposed to Giant Hogweed:

  • Wash the affected area immediately with soap and water
  • Keep the area out of the sun for at least 48 hours
  • Seek medical advice for burns

Giant Hogweed, originally planted in domestic gardens as an ornamental feature plant, has spread throughout the Lower Mainland and can be found in ravines, open wood areas, roadside ditches and riparian areas.

A member of the Asian parsley or carrot family, Giant Hogweed closely resembles our native plant cow parsnip, except its taller, growing up to 6 metres or more.

Giant Hogweed has numerous small white flowers clusters in an umbrella-shaped head, with stout, hollow green stems covered in purple spots. Dark green leaves are coarsely toothed in three large segments with stiff underside hairs, and lower leaves can exceed 2.5 metres in length. Giant Hogweed can reach up to 6 metres in height and each plant produces up to 100,000 winged seeds that are viable for up to 15 years.

Giant Hogweed is a highly competitive plant due to vigorous early-season growth, tolerance of full shade and seasonal flooding, as well as its ability to co-exist with other aggressive invasive plant species. In the winter months, when the leaves die back, the soil is exposed to winter rains causing erosion in adjacent streams.

If you find Giant Hogweed on your property:

Due to health concerns, residents are not advised to handle Giant Hogweed plant material. Instead, contact the BC Landscape and Nursery Association to find a contractor to remove the plant on your property. Please note, removed plant parts should be disposed on in a sealed garbage bag and not placed in the City's Green Can program.

Giant Hogweed Links:

Japanese Knotweed

Japanese KnotweedIntroduced from Asia in the 1800's, Japanese Knotweed was considered an attractive and harmless shrub. However, through the ever-increasing disturbance of natural areas, this aggressive perennial soon established its invasive foothold. Reaching heights of up to 3.3m (10 ft) tall, Japanese Kknotweed has the ability to over-shadow and out-compete all plants within its reach, reducing the ecological integrity of an area.It can now be found growing anywhere including waste sites, along roads, in meadows and wooded areas and along streambanks.

It has small green-white flowers grow in showy plumes off stem and leaf joints. Its stems are hollow and bamboo-like, with reddish-brown speckles. The leaves are heart-shaped and 8-10 cm across and there is a zig-zag pattern of leaf arrangement on the stem. It can grow over 3m in a year.

If allowed to grow unmanaged the plant can grow into dense monocultures which contribute to:

  • Slope instability and increased erosion of stream banks.
  • Over widening of stream/ditches which undercut existing roadways.
  • Damage to asphalt, tarmac, sewerage and infrastructure.
  • Degradation of environmental values like poor water quality and decline of native birds, insects and plants.

Knotweed can grow through cement, house foundations, and walls. Its extensive root systems are capable of re-sprouting even after many years of control and roots can break off and float downstream to form new infestations.

Knotweed Links:

City Actions

The City’s management approach uses multiple tools in our invasive management toolbox, including:

  1. Education & Outreach
  2. Control
    • Hogweed and knotweed control contractors – only herbicide treatment in the City*
    • City crew activities – manual control of English ivy (especially cut from trees), Clematis, Hops, Scotch broom, English holly
  3. Stakeholder Coordination
    • Collaborating with other agencies, including the Districts of North and West Vancouver, Metro Vancouver, BC Parks, BC Hydro, Squamish Nation, and the Provincial Ministry of Transportation
    • Actively involved in the development of the Regional Invasive Species Management Strategy & an active participant in Metro Vancouver’s Invasive Species Task Force
  4. Assessment & Restoration
  5. Adaptive Management
  • On-going monitoring & follow-up will be the key to successful management
  • The City has developed AlienMap, an internal web application for tracking all control efforts.

The City uses an Integrated Pest Management (IPM) approach when managing invasive species.  This includes extensive monitoring and both manual and chemical (herbicide) control treatment. Limited applications of herbicide (glyphosate) are used for hogweed and knotweed only, because manual removal of these plants can be more damaging to the habitat than the use of a targeted herbicide. For example, knotweed can grow up to 3 meters below grade and up to 20 metres laterally.  Small fragments of knotweed the size of a thumbnail, if left behind in the soil, can easily regenerate.  Herbicides and other pesticides are not otherwise used in the maintenance of the City’s parks and natural areas.

Inventory Update

In 2011, the City completed a baseline inventory of City owned lands. This snap shot provided the basis for the 2013 Invasive Plant Management Strategy. In 2015, the City completed an update of the inventory. Results from the inventory show a major reduction in abundance and distribution of Giant Hogweed (91% reduction) and Knotweed species (71% reduction).

2011 (m2) 2015 (m2) % Change
Giant Hogweed 1,038 93 -91%
Knotweed 7,728 2,248 -71%

 

Additional results from the inventory update show:

  • reductions in Scotch broom, butterfly bush, hops, policeman’s helmet and Japanese butterbur
  • no new provincially listed noxious weed species - species listed under the B.C. Weed Control Act
  • no emergent species of major concern, including Early Detection Rapid Response (EDRR species are new invasive species requiring a rapid control response)
  • significant natural areas cleared of invasive plants and restored with native vegetation
  • removal of climbing ivy and clematis from hundreds of impacted trees thus preventing future tree canopy loss. Only a small number of trees remain impacted
  • few new illegal green waste dump sites

The 2015 inventory update will be used to inform invasive plant management work over the next five years. As the City continues to reduce hogweed and knotweed density and distribution, efforts will be shifted to management of other priority species and towards increased planting and rehabilitation of impacted areas.

Goals

Strategy Goals

The City’s Invasive Plant Management Strategy, adopted by Council in 2013, guides the management of invasive plants on public lands and facilitates the management of invasive plants on private lands. The purpose of the Invasive Plant Management Strategy (Strategy) is to provide the City with an efficient, cost effective, coordinated approach to managing invasive plants.

The goals of the Invasive Plant Management Strategy are to have an effective, adaptable strategy that will:

  1. Outreach and Education: Increase awareness & knowledge of invasive plants within the community;
  2. Control Implementation: Measurably reduce invasive plant density & distribution;

  3. Stakeholder Coordination: Coordinate efforts between all stakeholders & resources;

  4. Assessment and Restoration: Effectively monitor, maintain & restore the City’s parks and natural areas; and

  5. Policy and Adaptive Management: Develop effective policy and practice adaptive management.

If left unchecked, invasive plant species will continue to spread and further degrade the environment, cause detrimental economic impacts and pose human health risks. By implementing the actions identified in the Strategy the City is anticipated to achieve the goals and thus ensure safe, sustainable, and ecologically healthy areas for the benefit of future generations.

Top Priority Species

Top Priority Species

Noxious weeds are invasive species recognized by the BC government as highly destructive, competitive, and difficult to control. Like other invasive species, they are non-native plants that have been introduced to BC without the predators that help keep them in check in their native habitats. The BC Weed Control Act imposes a duty on all land owners to control designated noxious weeds. As such, the City is required under the BC Weed Control Act to control these species.

In 2011, eighteen species were added as provincially noxious under the B.C. Weed Control Act, including the following species significant to the City:

  • Giant hogweed (Heracleum mantegazzianum)
  • Knotweed, Bohemian (Fallopia bohemica)
  • Knotweed, Giant (Fallopia sachalinensis)
  • Knotweed, Himalayan (Polygonum polystachyum)
  • Knotweed, Japanese (Fallopia japonica)

Due to this designation, combined with the results of the Invasive Inventory, Giant Hogweed and knotweed species have been identified as the City's highest priority species. These species pose public health risks, present slope stability concerns, and can damage buildings and infrastructure.

 

Giant Hogweed

Giant HogweedWARNING: The stem and stem hairs of the Giant Hogweed exude a clear watery sap, which sensitizes the skin to ultraviolet radiation. Exposure to this sap can result in severe burns and blistering to the affected areas. If you are exposed to Giant Hogweed:

  • Wash the affected area immediately with soap and water
  • Keep the area out of the sun for at least 48 hours
  • Seek medical advice for burns

Giant Hogweed, originally planted in domestic gardens as an ornamental feature plant, has spread throughout the Lower Mainland and can be found in ravines, open wood areas, roadside ditches and riparian areas.

A member of the Asian parsley or carrot family, Giant Hogweed closely resembles our native plant cow parsnip, except its taller, growing up to 6 metres or more.

Giant Hogweed has numerous small white flowers clusters in an umbrella-shaped head, with stout, hollow green stems covered in purple spots. Dark green leaves are coarsely toothed in three large segments with stiff underside hairs, and lower leaves can exceed 2.5 metres in length. Giant Hogweed can reach up to 6 metres in height and each plant produces up to 100,000 winged seeds that are viable for up to 15 years.

Giant Hogweed is a highly competitive plant due to vigorous early-season growth, tolerance of full shade and seasonal flooding, as well as its ability to co-exist with other aggressive invasive plant species. In the winter months, when the leaves die back, the soil is exposed to winter rains causing erosion in adjacent streams.

If you find Giant Hogweed on your property:

Due to health concerns, residents are not advised to handle Giant Hogweed plant material. Instead, contact the BC Landscape and Nursery Association to find a contractor to remove the plant on your property. Please note, removed plant parts should be disposed on in a sealed garbage bag and not placed in the City's Green Can program.

Giant Hogweed Links:

Japanese Knotweed

Japanese KnotweedIntroduced from Asia in the 1800's, Japanese Knotweed was considered an attractive and harmless shrub. However, through the ever-increasing disturbance of natural areas, this aggressive perennial soon established its invasive foothold. Reaching heights of up to 3.3m (10 ft) tall, Japanese Kknotweed has the ability to over-shadow and out-compete all plants within its reach, reducing the ecological integrity of an area.It can now be found growing anywhere including waste sites, along roads, in meadows and wooded areas and along streambanks.

It has small green-white flowers grow in showy plumes off stem and leaf joints. Its stems are hollow and bamboo-like, with reddish-brown speckles. The leaves are heart-shaped and 8-10 cm across and there is a zig-zag pattern of leaf arrangement on the stem. It can grow over 3m in a year.

If allowed to grow unmanaged the plant can grow into dense monocultures which contribute to:

  • Slope instability and increased erosion of stream banks.
  • Over widening of stream/ditches which undercut existing roadways.
  • Damage to asphalt, tarmac, sewerage and infrastructure.
  • Degradation of environmental values like poor water quality and decline of native birds, insects and plants.

Knotweed can grow through cement, house foundations, and walls. Its extensive root systems are capable of re-sprouting even after many years of control and roots can break off and float downstream to form new infestations.

Knotweed Links:

City Actions

City Actions

The City’s management approach uses multiple tools in our invasive management toolbox, including:

  1. Education & Outreach
  2. Control
    • Hogweed and knotweed control contractors – only herbicide treatment in the City*
    • City crew activities – manual control of English ivy (especially cut from trees), Clematis, Hops, Scotch broom, English holly
  3. Stakeholder Coordination
    • Collaborating with other agencies, including the Districts of North and West Vancouver, Metro Vancouver, BC Parks, BC Hydro, Squamish Nation, and the Provincial Ministry of Transportation
    • Actively involved in the development of the Regional Invasive Species Management Strategy & an active participant in Metro Vancouver’s Invasive Species Task Force
  4. Assessment & Restoration
  5. Adaptive Management
  • On-going monitoring & follow-up will be the key to successful management
  • The City has developed AlienMap, an internal web application for tracking all control efforts.

The City uses an Integrated Pest Management (IPM) approach when managing invasive species.  This includes extensive monitoring and both manual and chemical (herbicide) control treatment. Limited applications of herbicide (glyphosate) are used for hogweed and knotweed only, because manual removal of these plants can be more damaging to the habitat than the use of a targeted herbicide. For example, knotweed can grow up to 3 meters below grade and up to 20 metres laterally.  Small fragments of knotweed the size of a thumbnail, if left behind in the soil, can easily regenerate.  Herbicides and other pesticides are not otherwise used in the maintenance of the City’s parks and natural areas.

Inventory Update

Inventory Update

In 2011, the City completed a baseline inventory of City owned lands. This snap shot provided the basis for the 2013 Invasive Plant Management Strategy. In 2015, the City completed an update of the inventory. Results from the inventory show a major reduction in abundance and distribution of Giant Hogweed (91% reduction) and Knotweed species (71% reduction).

2011 (m2) 2015 (m2) % Change
Giant Hogweed 1,038 93 -91%
Knotweed 7,728 2,248 -71%

 

Additional results from the inventory update show:

  • reductions in Scotch broom, butterfly bush, hops, policeman’s helmet and Japanese butterbur
  • no new provincially listed noxious weed species - species listed under the B.C. Weed Control Act
  • no emergent species of major concern, including Early Detection Rapid Response (EDRR species are new invasive species requiring a rapid control response)
  • significant natural areas cleared of invasive plants and restored with native vegetation
  • removal of climbing ivy and clematis from hundreds of impacted trees thus preventing future tree canopy loss. Only a small number of trees remain impacted
  • few new illegal green waste dump sites

The 2015 inventory update will be used to inform invasive plant management work over the next five years. As the City continues to reduce hogweed and knotweed density and distribution, efforts will be shifted to management of other priority species and towards increased planting and rehabilitation of impacted areas.

See the Invasive Plant Species List

 

WHAT CAN YOU DO?

Here are some things that you can do:

  • Never dump garden waste or hanging baskets into parks or other natural areas.
  • Dispose of all plant material through the City's Green Can Program (except Hogweed).
  • Avoid buying plants promoted as fast spreaders or vigorous self-seeders. These are often invasive.
  • Contain or remove invasive plants on your property to prevent them from spreading.
  • Control weeds that grow under bird feeders. The falling birdseed can become a source of invasive plants.
  • Use caution when ordering plant seeds over the internet or through catalogues. The introduction of foreign seeds is a significant route for invasive plants to find their way into the City.
  • Grow native plants in your garden – for more information contact the Native Plant Society of British Columbia.
  • Read the Grow Me Instead Brochure to learn about BC's most ’unwanted’ plants, along with recommended alternatives.
  • GET INVOLVED - Check out the volunteering opportunities with the City Park Stewards and other community groups in the City.



Contact Info

Angela Negenman
Environmental Technician
Phone: 604-982-3932
Email: anegenman@cnv.org

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