Smart Gardening and Invasives

Knotweed | Giant Hogweed | European Fire Ant

Invasive (“alien”) species are non-native species that have been introduced and have spread into a new area often unintentionally by human activity (e.g., as a garden ornamental).  Invasive species can cause significant ecological, economic and environmental damage and can out-compete native species and form monocultures that reduce ecosystem complexity and stability. Typical pathways of spread include the sharing of plants, or the deposit of soil or green waste. For instance, invasive species are commonly introduced into city parks and natural areas – such as Glenbrooke ravine or South Dyke Road riparian zone – through the illegal dumping of green waste from spent ornamental planters. 

The City is training staff to identify common invasive species and share new practices to prevent their spread.  In particular, the most aggressive invasive plant species are being inventoried and targeted for removal and control.  These plants – which are of high concern and provincially classified as “noxious” – include Giant Hogweed (Heracleum mantegazzianum) or the Knotweed species (Fallopia sp.).  The most important insect invasive species include the European Chafer Beetle and more recently the European Fire Ant.   More detailed information on these invasive species is outlined below.

There are also a number of non-noxious invasive species found in New Westminster.  The city has been active in supporting local community groups in the removal of these invasive plants in the City:

• Himalayan blackberry (Rubus discolor)
• English ivy (Hedera helix),
• Scotch Broom (Cytisus scoparius)
• Policeman’s Helmet (Impatiens glandulifera)
• Yellow Lamium (Lamium galeobdolon)
• Morning Glory (Convolvus arvensis)
• Purple Loosestrife (Lythrum salicaria)

For further information on the best management practices for Giant Hogweed in the Metro Vancouver Region, please click here

Knotweed species

Knotweeds are aggressive invasive perennial plants.  Four species are found in British Columbia: Japanese knotweed (Fallopia japonica); Bohemian knotweed (Fallopia x bohemica); Giant knotweed (Fallopia sachalenensis); and Himalayan knotweed (Polygonum polystachyum). They can be identified by their hollow, bamboo-like stems with distinct red- coloured segments, large green leaves and small creamy-white flowers that form clusters.   Knotweed spreads quickly and has caused environmental and economic impacts such as reducing plant biodiversity (competes with native vegetation), causing erosion, clogging waterways or by pushing through infrastructure such as asphalt, concrete and home foundations.  It is capable of growing four centimetres a day, and if left untreated, the plant can spread 20 metres wide and three metres high and three metres deep underground.

Residents are asked not to cut, mow or compost knotweed as any tiny root or stem fragment left behind can result in further growth.  Land owners or occupiers must control designated noxious plants on their property, as knotweed was added to the list of noxious weeds in BC (BC Weed Control Act). The most effective way to manage knotweed is to use specially-selected herbicide which attacks the knotweed’s extensive root system.  Land owners should call a company with certified applicators. They can help you choose the appropriate treatment method for your property and get the job done safely (note:  the BC Weed Control Act supersedes the City’s local pesticide use bylaw for species listed on the BC noxious plant list).

For further information on the best management practices for Knotweed in the Metro Vancouver Region, please click here.

To report any sightings of knotweed on City property, please call the City at 604-521-3711.

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Giant Hogweed

Giant hogweed is a toxic, noxious weed that can be identified by its reddish-purple stem with fine spines, and its spotted leaf stalks. The plant can grow up to 16ft (5m) high, has leaves up to 5ft (1.5m) wide, and numerous small white flowers clusters in an umbrella-shaped head. Hogweed is often confused with similar looking but the much smaller species, Cow Parsnip or Queen Anne’s Lace.  The plant typically grows on riverbanks, ravines, vacant lots or along roads, but can also occur on residential property.

Removal and Disposal
If you find Giant Hogweed on your property, it needs to be removed as per the City's Unsightly Premises Bylaw No. 5969, 1991. The BC Weed Control Act also imposes a duty on all land occupiers to control designated noxious plants.

It is best to let a professional remove this plant.  CAUTION - If you are going to remove the plant yourself, always wear protective, waterproof clothing, gloves and safety goggles and follow Work Safe BC instructions on their safety bulletin and video.  Never compost the plant or put in your Cleaner, Greener Bin. Dispose of all plant parts in double-bagged garbage bags (preferably clear) and put out for curbside collection. Do not transfer soil from within four metres of the plant as the soil may contain Giant Hogweed seed. Continue to monitor the area for several years.

If you are exposed to Giant Hogweed, wash the affected area immediately, keep it out of the sun and seek medical advice.  If you find Giant Hogweed on your property, please contact the Invasive Species Council of Metro Vancouver at 604-880-8358.

To report any sightings on City property, please call Engineering Operations at 604-526-4691.  Please confirm that you have Hogweed and not the smaller unrelated species:  Cow Parsnip or Queen Anne’s Lace.

For information on Giant Hogweed in our region, please visit  the Invasive Species Council of BC page or view Metro Vancouver’s Best Management Practices for Giant Hogweed.

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European Fire Ant

The European Fire Ant (Myrmica rubra) is an aggressive, swarming ant that can deliver a painful sting when disturbed. It was first found in BC in 2010 and since then their presence has been confirmed in several isolated locations across the lower mainland, Fraser Valley and Vancouver Island.

BC’s irrigated lawns and gardens, coupled with a moderate coastal climate, make for ideal conditions for fire ants to establish dense colonies. The ant is introduced into new environments through garden and landscape materials, such as potted plants, mulch and soil. If you are purchasing plants, soils or mulch it is important that you inspect the material to make sure you are not carrying the ants. 

There is not yet an effective method for eradicating European fire ants; however, there are a number of approaches that could minimize impacts and prevent their spread.  For more information on the European Fire Ant, please visit the BC Inter-Ministry Invasive Species Working Group website.

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