Canadian Council on Invasive Species | CCIS

Read Highlights of the National Invasive Species Forum

Ottawa | Feb 28 - Mar 2, 2017

Canadian Council

on Invasive Species

Canadian Council

on Invasive Species

Canadian Council

on Invasive Species

Canadian Council

on Invasive Species

Canadian Council

on Invasive Species

Canadian Council

on Invasive Species

Canadian Council

on Invasive Species

Canadian Council

on Invasive Species

Canadian Council

on Invasive Species

Canadian Council

on Invasive Species

Canadian Council

on Invasive Species

Canadian Council

on Invasive Species

Canadian Council

on Invasive Species

Canadian Council

on Invasive Species

Canada’s Top 10 Most Important Invasive Horticultural Plants

1.    Leafy spurge

Scientific name: Euphorbia esula

  • One of the most frequently identified “most unwanted” invasive plants across Canada
  • Grows wild across Canada (recorded in all provinces/territories except Newfoundland, NWT and Nunavut).
  • Six provinces (BC to Ontario, plus NB) and two territories (Yukon and NWT) recommend that gardeners not grow or plant leafy spurge 
  • The reasons gardeners love it are also the reasons it is highly invasive: persistent, competitive, spreads easily via seeds and extensive root system, prolific seed producer
  • Provincially regulated in Ontario, BC and Alberta as a noxious weed
  • Federally regulated as a Prohibited Noxious Weed by the Seeds Act in order to control its spread and limit its occurrence in agricultural fields

Resources 


2.    Flowering rush
(aka: Grassy rush, Water gladiolus) 

Scientific name: Butomus umbellatus

  • One of the most frequently identified “most unwanted” invasive plants across Canada
  • Grows wild along the edges of lakes and rivers in southern Canada from British Columbia to Prince Edward Island, with most large populations occurring in eastern Canada 
  • Eight provinces in southern Canada, from BC to PEI (except Nova Scotia and Newfoundland) recommend that gardeners not grow or plant flowering rush.
  • Prized as an aquatic garden plant for its tall and beautiful pale pink flowers and faint scent. The plant is still sold by nurseries across North America.
  • Provincially regulated in BC, Alberta and Saskatchewan as a noxious weed

Resources 


3.    Oxeye daisy
(aka Marguerite commune) 

Scientific name: Leucanthemum vulgare
Synonym: Chrysanthemum leucanthemum

  • Commonly grows along roadsides and in meadows, revealing showy white flowers in the summer months
  • Despite the problems this plant causes in agricultural fields, reducing the quality of pastures by outcompeting grasses, it is still commonly found in wild flower seed mixes. The plant is also not favoured by grazing animals due to an unpleasant taste.
  • It is a prolific seed producer and seeds may survive ingestion and burial for several years, but the plant also spreads via underground stems.
  • Two territories (Yukon and NWT) and all five provinces from BC to Ontario recommend that gardeners not grow or plant oxeye daisy. 
  • Provincially regulated as a noxious weed in Alberta
  • Federally regulated as a Primary Noxious Weed by the Seeds Act in order to control its spread and limit its occurrence in agricultural fields

Resources 


4.    Purple loosestrife

Scientific name: Lythrum salicaria

  • Grows abundantly across North America along river and lake shorelines and at the borders of wetlands
  • All five provinces from BC to Ontario, plus PEI recommend that gardeners not grow or plant purple loosestrife. 
  • An escaped ornamental that thrives in wild habitats where it can crowd out native vegetation 
  • Provincially regulated in BC and Alberta as a prohibited noxious weed. It is also the only regulated invasive plant in Prince Edward Island.
  • Federally regulated as a Primary Noxious Weed by the Seeds Act 

Resources 


5.    Himalayan Balsam
(aka Purple or Ornamental Jewelweed, Poor Man’s Orchid, Policeman’s helmet, Impatiente glanduleuse)

Scientific name: Impatiens glandulifera

  • Originally from the western Himalayas, it has escaped cultivation in Europe, North America, Asia and New Zealand
  • The plant is abundant in eastern Canada, but is also a garden escape in Saskatchewan and BC
  • A showy annual plant that thrives in moist soils along rivers, wetlands and riparian habitats. Flowers have a sweet floral scent that is attractive to pollinators. 
  • Plants grow aggressively each season shading out native vegetation and producing copious amounts of seed that are viable for more than one year and can disperse large distances from each plant
  • All six provinces from BC to Quebec, plus PEI recommend that gardeners not grow or plant this species
  • Provincially regulated in Alberta as a prohibited noxious weed

Resources 


6.    Yellow flag iris
(aka Pale yellow iris, Yellow iris, Water flag, Semences de fleurs sauvages) 

Scientific name: Iris pseudacorus

  • Introduced to North America as a pond ornamental for its showy, bright yellow flowers and use in erosion control owing to aggressive root and tuber growth. The plant continues to be advertised as a pond ornamental for sale today.
  • Growing in wetlands along freshwater and brackish shorelines, its below ground growth can alter the topography and water dynamics of a habitat
  • Grows wild in eastern Canada from Manitoba to Newfoundland, as well as in southern BC
  • All six provinces from BC to Quebec, and PEI recommend that gardeners not grow or plant this species
  • Provincially regulated in BC and Alberta as a prohibited noxious weed

Resources 


7.    Dalmatian toadflax
(aka Linaire de Dalmatie) 

Scientific name: Linaria dalmatica
Synonym: Linaria genistifolia ssp. dalmatica

  • Pretty yellow flowers on this relatively short plant look similar to snapdragons 
  • As a hardy perennial, the plant is a popular wildflower, but has escaped into roadsides, disturbed areas, meadows and cultivated fields
  • Plants are toxic to grazers, but livestock tend to avoid eating plants
  • Similar to many other escaped ornamental plants, each plant produces many flowering stems and spreads via seeds and horizontal roots
  • Occurs across Canada, including Yukon territory, but only identified as an “unwanted” invasive ornamental plant in four provinces in western Canada from Saskatchewan to BC, as well as in two territories, Yukon and NWT.
  • Native to the Mediterranean
  • Provincially regulated as a noxious weed in Alberta, and as a Prohibited weed in Saskatchewan
  • Federally regulated as a Primary Noxious Weed by the Seeds Act 
  • Close relative, L. vulgaris (butter and eggs, yellow toadflax) is also invasive in Canada (and unwanted from BC to Saskatchewan, as well as in NWT)

Resources 


8.    Creeping bellflower

Scientific name: Campanula rapunculoides

  • Perennial plants produce pretty bluebells (nodding flowers), can tolerate a range of light conditions and tolerate drought 
  • Roots grow aggressively and have a great capacity to spread beyond gardens and yards into neighbouring habitats, including growing under cement to reach suitable soils
  • Grows wild in all Canadian provinces from BC to Newfoundland
  • Growers in six provinces are advised to not choose this plant for their gardens, including Alberta, Saskatchewan, Manitoba, Ontario, New Brunswick and PEI
  • Provincially regulated as a noxious weed in Alberta

Resources 


9.    Dame’s rocket
(aka Sweet rocket, Dame’s violet) 

Scientific name: Hesperis matronalis

  • A member of the mustard family, the plant is commonly found growing in dense patches in ditches and other non-xeric disturbed areas throughout North America
  • Plants are biennials and produce clusters of evening fragrant white, pink or purple flowers throughout the summer
  • A popular seed in wildflower mixes
  • Growers in six provinces are advised to not choose this plant for their gardens, including Alberta, Saskatchewan, Manitoba, Ontario, Quebec and PEI

Resources 


10.    Common tansy

Scientific name: Tanacetum vulgare

  • A robust perennial with attractive button-like, and flat-topped yellow flowers
  • Has spread across Canada since its likely introduction 400 years ago, and now grows wild from Yukon to Newfoundland 
  • Leaves produce a chemical that has been used in traditional herbal medicines, but may be toxic to grazers and humans, and affects taste of milk produced by dairy cattle
  • Still sold in nurseries and is available as a herbal remedy
  • Provincially regulated as a noxious weed in Alberta, and regionally regulated as a noxious weed in British Columbia

Resources