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".
For further information regarding the impacts of invasive plants and weeds, visit BC Invasives.ca.
The Top 10 Most Unwanted Invasive Plants in the North Okanagan |
|
|---|---|
|
Image
Photo: Justin DeMerchant, ISCBC |
Hoary AlyssumBeteroa incana Hoary alyssum (False hoary madwort, Hoary berteroa) is a flowering plant with clusters of small white flowers with deeply notched petals. It spreads quickly through a long season of seed production. Seeds are dispersed by vehicles, equipment, footwear, wildlife, and birds. |
|
Image
Photo: S. Dewey |
CheatgrassBromus tectorum Cheatgrass (Downy brome, Drooping brome) is an annual grass introduced to North America in the late 1800’s with hairy leaves and drooping spikelets. It can be found alongside roads or disturbed areas, or in sagebrush ecosystems where it can form dense stands and outcompete native grasses. It can dramatically alter wildfire regimes, as well as injure livestock and animals’ eyes and mouths by its sharp awns. |
|
Image
Photo: L. Scott |
Sulphur CinquefoilPotentilla recta |
|
Image
Photo: Justin DeMerchant, ISCB
|
Purple LoosestrifeLytrhum salicaria Purple loosestrife (Spike loosestrife, Purple lythrum) is a perennial shrub-like plant with a showy spike of, purple-pink flowers and narrow, stalkless leaves. It spreads rapidly by seed and root fragments. The tiny seeds are dispersed by wind, mud, moving water, wildlife and humans. |
|
Image
Photo: M. Blackmore |
Myrtle spurgeEuphorbia myrsinites Myrtle spurge (Donkey tail, Blue spurge) is a short, creeping escaped garden perennial with oval, spiraling blue green stems and yellow-green flowers. It likes dry, disturbed soils where it grows quickly and aggressively, releasing chemicals from its roots which stop other plants from growing near it. |
|
Image
Photo: A. Smith |
Tree of heavenAilanthus altissima Tree of heaven (Ailanthus, Varnish tree) is a deciduous tree that can reach 20-30m in height, with small white flowers and oval shaped leaflets. It became popular in BC with gardeners for its rapid growth and interesting foliage. It produces by seed and by division and can sprout nearly anywhere, making it very difficult to eradicate! |
|
Image
Photos: R. Mueller |
Spotted Knapweed and Diffuse Knapweed
Spotted knapweed (Centaurea stoebe) grows 60-150 cm tall with several branched stems growing vertically from a thick taproot. Flowers are purple, sometimes white, found individually at the ends of branches. Black-tipped flower head bracts give plants a spotted appearance. Grey-green leaves are deeply lobed and become smaller as they advance up the stem. Diffuse knapweed (Centaurea diffusa) is a short flowering plant that grows up to 60 cm tall. Flowers are white or sometimes purple, found in clusters or solitary at the end of branches with small, sharp, rigid spines on the bracts. Leaves are hairy, grey-green, and split on many branches growing from a single upright stem |
|
Image
Photo: J. Hallworth |
Garlic MustardAlliaria petiolata Garlic mustard is a noxious weed growing prolifically in certain areas of the Regional District of the North Okanagan, most notably in Coldstream. Garlic mustard is a biennial plant – in the first year, plants appear as a rosette of green leaves close to the ground that develop into mature flowering plants the following spring. It can be found growing both in disturbed ecosystems, and in undisturbed forests as it is a shade-tolerant plant. It reproduces by seed only and is unpalatable for herbivore grazers. Garlic mustard outcompetes native plants, and in a previously uninvaded forest, it can become the dominant understory plant in 5-7 years. Garlic mustard grows from 20–100 cm tall. Flowers are small and white with four petals arranged in a cross-like shape. The fruit is a pod containing two rows of shiny black seeds. Leaves are triangular to heart-shaped, with a coarsely toothed margin. Crushed leaves, and especially the S-shaped taproot, give off a garlic smell. |
|
Image
|
Yellow IrisIris pseudacorus Yellow flag Iris is a provincial noxious weed in British Columbia and is found throughout the Regional District of the North Okanagan. Yellow flag Iris is often purchased as an ornamental, but can easily escape gardens and invade ditches, wetlands, streams, lake shorelines, and shallow ponds. This plant reproduces through seed dispersal, horizontal roots, and when pieces of the roots break off, which can form new plants. The seeds float on the water in spring and fall, causing them to spread quickly. Several hundreds of plants may be connected underwater due to the extensive root system, which creates a thick mat that damages wildlife habitat, reduces water flow, and crowds out native vegetation. This perennial aquatic plant can grow to be 1-1.5 m tall on a smooth green stem. Flowers are bright yellow, often with brown spots or purple veins. Leaves are flat and sword-shaped, up to 90 cm long and 3 cm wide. |