Invasive Weeds

An invasive species is a nonnative species whose introduction causes (or is likely to cause) economic harm, environmental harm, or harm to human health. These species grow and reproduce rapidly, causing major disturbance to the areas in which they are present. Only a small percentage of nonnative species are invasive, but that small percentage causes a great deal of damage.

City employees will be picking and spraying for noxious plants and residents are asked to do the same on their own properties. Please make efforts to remove all of these invasive plants from your yard and alley to prevent their spread. 
 
Some weeds that have been found in Camrose are: 
 
  • Prohibited Noxious: Himalayan Balsam.
  • Noxious: Baby’s Breath, Creeping Bellflower, Dame’s Rocket, Scentless Chamomile, Oxeye Daisy, Canada Thistle, White Cockle, Yellow Clematis. 
Information on all these weeds can be found at www.abinvasives.ca.

Himalayan Balsam


Impatiens glandulifera Himalayan Balsam
Also called poor man’s orchid, policeman’s helmet, Indian balsam, touch-me-not, and ornamental jewelweed. This annual germinates in disturbed soil and grows quickly up to 3m tall to shade-out competing native vegetation. Stems are smooth, tinged red-purple, and are hollow. Leaves are 6-15 cm long with sharply serrated edges. Large pink to purple flowers grow in groups of 5-10. The 5 petals form a hood over the center of the flower as well as a landing platform for pollinators. Hand-pull then bag plants and avoid buying under any of the names above.

Baby’s Breath


Gypsophila paniculata Babys Breath
Native to central Eurasia and introduced as an ornamental and for use in the floral industry. It is also called maiden’s breath and can have white, pink, or maroon flowers. The small, airy, 5-petaled flowers grow on highly branched stalks that can grow up to 1m tall. When pulling, it is important to remove as much of the long tap root as possible to prevent regrowth. To prevent spread, do not grow it and carefully dispose of floral arrangements containing this plant.
 

Creeping Bellflower


Campanula rapunculoides Creeping Bellflower
Introduced from Europe as an ornamental and in wildflower seed mixes. Stems grow to 1m tall with alternate 3-7cm leaves. The nodding flowers are light purple and composed of 5 petals growing along one side of the stem. Similar to the native harebell, which is much shorter, with smaller flowers and leaves. Cutting flower spikes before bloom can limit the spread of seeds, but digging up the root system is necessary to remove the plant. Only buy seed mixes that list the contents and are free of invasive species.

Dame’s Rocket


Hesperis matronalis Dames Rocket
A member of the mustard family from Europe and southwest Asia introduced as a fragrant ornamental and in wildflower mixes under the alternate names of dame’s violet and sweet rocket. Stems grow 0.5 to 1m tall with alternate lance-shaped leaves. Clusters of flowers on the tops of stems are white to purple with 4 petals, distinguishing it from native garden phlox, which has 5. Roots should come out easily with hand pulling, although yearly removal may be necessary until all seeds in the soil are exhausted.

Scentless Chamomile


Tripleurospermum perforatum, T. inodorum Scentless Chamomile
Very similar to oxeye daisy, which is also a weed. No other white-flowered daisy is native to Alberta. Stems up to 1m tall grow very fine leaves and flowers with a yellow central disk and many white petals. Scentless chamomile does not compete well with other healthy plants. To remove existing plants, hand pull, then burn or bag to prevent spreading seed.

Oxeye Daisy


Leucanthemum vulgare, Chrysanthemum leucanthemum Oxeye Daisy
Very similar to scentless chamomile, which is also a weed. No other white-flowered daisy is native to Alberta. A close relative, Shasta daisy, is sold from nurseries and in wildflower mixes and can cross breed with the oxeye. Stems grow up to 1m tall with lance-shaped leaves and flowers have a yellow center with many white petals up to 5cm in diameter. Hand-pull before flowering needs to be repeated yearly to exhaust seeds in the soil. The roots must also be dug up. Biological controls are being investigated. 

Canada Thistle


Cirsium arvense Canada Thistle
Introduced from Europe, this thistle forms large colonies of woody, hollow stems that grow up to 1.5m tall and can have a large effect on natural ecosystems. Leaves are dark green and shiny, many with sharp spines. Clusters of urn-shaped flower heads at the ends of stems produce white to purple flowers. Maintaining healthy plant cover can prevent establishment of thistle, but large roots make it very difficult to remove. Repeated mowing can stress the plant, as can removal of parts of the root system. Biological controls are being investigated.

White Cockle


Lychnis alba, Silene alba, Silene latifolia White Cockle
Introduced from Eurasia and is an extremely heavy seed producer, causing problems when it spreads into agricultural fields. Hairy stems grow 30-120cm tall and have opposite leaves which are also hairy. Numerous clusters of white to pink flowers have 5 flowers and open in the evening. All parts of the root and stem must be removed to prevent regrowth. Mowing will also reduce seed production.

Yellow Clematis


Clematis tangutica Yellow Clematis
Has many other names including Golden Clematis, Golden Tiara, Virgins-Bower, Radar Love, and Helios. This vine from high-altitude China and India can grow rapidly across the ground, along fences, and up trees. The stems start out green but become tough and woody, with compound, pointed leaves. The bright yellow flowers are bell-shaped, turning into seeds which have white silky tails. This plant is spread primarily through nurseries and can be controlled by repeatedly removing the vines and the long tap root.