Invasive Plants and Noxious Weeds

Invasive plants are typically non-native plants or "weeds" that have been introduced to British Columbia without the insect predators and plant pathogens that help keep them in check in their native habitats. Without their natural enemies, these invaders are able to rapidly outcompete native plants, ornamental species and agricultural crops. The Ministry of Agriculture and Lands has classified some of the most harmful invasive plants as "noxious weeds".


Everyone's Problem! Invasive plants negatively impact our local environment and economy by:

  • reducing the agricultural productivity of our cropland and rangeland;
  • lowering real estate values;
  • endangering our health and well-being;
  • dramatically damaging some of the region's unique scenic values and tourism opportunities;
  • reducing water quality and fish habitat;
  • altering the composition and structure of native plant communities; and
  • destroying valuable wildlife habitat.
The Top 10 Most Unwanted Invasive Plants in the Okanagan-Similkameen
Blueweed

Photo Credit: L. Scott

Blueweed
https://www.oiso.ca/species/blueweed/

A biennial to short-lived perennial that grows 30-80 cm tall. Its bright blue blossoms bloom in May through to September. Individual seeds resemble the shape of a viper’s head. Blueweed invades pastures and rangelands, replacing forage plants, and can be toxic to livestock if ingested.  


Common Bugloss

Photo Credit: L. Scott

Common Bugloss (Anchusa)
https://www.oiso.ca/species/common-bugloss/

A biennial or perennial forb that grows 30-80 cm tall. Its tubular flowers are initially reddish and turn deep purplish blue, and bloom from May to July. Leaves are covered in stiff hairs. It can invade pastures, hay lands, alfalfa field, and rangelands, reducing crop yield.

Hoary Alyssum

Photo Credit: L. Scott

Hoary Alyssum
https://www.oiso.ca/species/hoary-alyssum/

An annual to short-lived perennial that grows 0.3 to 1.1 m tall. It has clusters of white flowers that bloom from late spring until the first frost. It can be very troublesome to ranchers, as horses can become intoxicated after eating green or dried hoary alyssum plants.  

Knotweed

Photo Credit: L. Scott

Knotweed

https://www.oiso.ca/species/knotweed/ 

 

A tall perennial that grows 1 to 5 m in height at maturity. It has small white-green flowers that grow in showy-plume like branched clusters, and hollow “bamboo-like” stems. Knotweeds can dominate riparian areas, threaten biodiversity, damage infrastructure, and disrupt recreation.

Leafy Spurge

Photo Credit: L. Scott

Leafy Spurge
https://www.oiso.ca/species/leafy-spurge/  

A perennial that grows up to 1 m tall. It has inconspicuous, greenish- yellow flowers and contains a milky latex sap. It displaces native vegetation and degrades grazing lands. It is extremely toxic to cattle.

Longspine Sandbur

Photo Credit: L. Scott

Longspine Sandbur
https://www.oiso.ca/species/longspine-sandbur/

An annual grass that grows 0.25 to 0.75 m tall, typically upright but can branch and spread flat along the ground. Its spiky burs can readily attach to humans and animals.

Puncturevine

Photo Credit: L. Scott

Puncturevine
https://www.oiso.ca/species/puncturevine/

An annual that grows along the ground and can reach 0.3 to 1.5 m long. Its small, yellow flowers appear from late spring or early summer until frost. It can form dense mats and produce fruits that are spiny and can hook into humans, animals, tires, and other surfaces.

Rush Skeletonweed

Photo Credit: L. Scott

Rush Skeletonweed
https://www.oiso.ca/species/rush-skeletonweed/

A heavily branched perennial that grows to 1.3 m tall. It has several wiry stems with stiff hairs, with small yellow flowers attached to the ends. Without control measures, rush skeletonweed can produce a mono-culture of interconnected plants that can become an entire colony.

Sulphur Cinquefoil

Photo Credit: L. Scott

Sulphur Cinquefoil
https://www.oiso.ca/species/sulphur-cinquefoil/

A perennial that grows 15-70 cm tall. Flowers are pale yellow with five-heart shaped petals, and bloom in mid-June throughout summer. Once established, this weed can produce dense populations that reduce or eliminate forage production and biodiversity.

Yellow Flag Iris

Photo Credit: L. Scott

Yellow Flag Iris
[Link: Missing for now- not yet uploaded to OISO ]

A perennial plant that grows up to 1.5 m tall. It has showy yellow flowers that bloom between April and July. It can form dense stands in wet areas that outcompete native species. It is also toxic to livestock and can cause skin irritation in people.  

Other Invasive Plants

Photo Credit: L. Scott

Other Invasive Plants
https://www.oiso.ca/species-category/terrestrial-plants/

Okanagan Invasive Species Online (OISO) is a collaborative, valley-wide project that shares information about invasive species specific to the region. Learn about more invasive plant species that threaten the Okanagan-Similkameen.