Weeds

Common Mullein (Verbascum thapsus) also known as Cowboy’s toilet paper due to its large, and very soft, felt-like leaves. This plant can be easily identified in its basal rosette stage or it’s erect flowering stem in the second stage of growth. The stems are woody and can grow up to 2.5 m tall, has a candle-stick appearance and from July to September you can see their 5-petaled, yellow flowers. This is a biennial plant in the Figwort/ Snapdragon family, native to Europe. This plant was used as a fish poison and brought over as a medicinal plant to treat an array of ailments but unfortunately has proven to displace native vegetation and overtake disturbed areas. Also, this plant is thought to serve as an alternate host for insects that negatively affect pear and apple trees. Common Mullein can produce up to 250,000 seeds per plant. The seeds generally don’t spread far from the plant but are viable for over 100 years making eradication difficult once established in an area. You can hand pull the entire plant but if there are flowers or seeds present you will want to bag and burn the flowered stems. The rosettes are easy to hand pull and can be controlled with herbicides.

Common Tansy (Tanacetum vulgare) is a perennial plant that was brought over as an ornamental from Europe. It is mildly toxic to humans and wildlife if consumed. You can identify these plants by their button-like yellow flowerheads that form dense clusters of 20-100 on the stem ends June through to September. Leaves have alternate arrangement; they are consistent in size and have deeply toothed margins giving it a fern-like appearance. These leaves will have a strong odour when crushed and were once used to deter insects and mice from corn bins. Stems are often purplish-red, erect, and woody. They can also be identified by their old woody skeletons from previous years. These plants prefer areas with full-sun and well-drained soil. You often see them roadside and along riparian areas. These plants can be upwards of 1.8 m tall and reproduce by seed and creeping roots. Common Tansy can produce up to 50,000 seeds which remain viable for up to 25 years. These plants can be controlled by cutting and mowing or destroyed by herbicide application.

Dalmatian Toadflax (Linaria dalmatica) is native to southeast Europe. The species name dalmatica, refers to the Dalmatia region of Croatia. Dalmatian toadflax is a short-lived perennial plant belonging to the Snapdragon family, flowering from June to September. It is mildly toxic to livestock and can reproduce by seeds or creeping roots. It has yellow snapdragon-like flowers with a darker yellow spot on the lower lip, sometimes appearing orange. The leaves are waxy, and are pale blueish green. The leaves are oval to heart shape with pointed tips and clasp the stem. This weed can grow to 120 cm tall and can have multiple branches growing off the stem. Dalmatian toadflax has a deep, woody taproot with horizontal roots that can form new plants and spread up to 500,000 seeds. Dalmatian toadflax’s flowers are almost identical to those found on Yellow Toadflax although the leaves are very different. Yellow toadflax leaves are lanced shaped and attached directly to the stem without clasping. Dalmatian Toadflax can grow in disturbed areas, grasslands, pastures, and residential areas. Repeated hand-pulling and herbicide are appropriate control measures for this weed. Dalmatian toadflax stem-boring weevil has been used as a bio control agent.

Leafy Spurge (Euphorbia virgata) is an aggressive weed toxic to livestock, humans and wildlife when consumed or when the milky sap touches the skin. Young leafy spurge can resemble noxious weed Yellow toadflax, which does not contain a milky sap. Leafy spurge is native to Asia and Europe and has unique disk shaped, yellow-green flowers from June to September. Leafy spurge is often found in pastures, grasslands, and aquatic areas. The stems can grow up to 90 cm tall and develop deep, extensive creeping lateral roots. Small seeds grow in pods that explode and scatter up to 130,000 seeds, 15 m in diameter. The milky sap has been known to cause temporary blindness and skin rashes so please handle with care. Leafy spurge can be controlled with herbicide, biocontrol leafy spurge beetles, repetitive mowing before seed set, or with sheep and goats. Leafy spurge is palatable to sheep and goats.

Perennial Sow Thistle (Sonchus arvensis) belongs to the Sunflower family. It is native to Europe and Asia and has been introduced to every province in Canada. Other common names for this plant include Creeping sow thistle, Field milk thistle, and Marsh sow thistle. The flowerheads can be easily confused with dandelions although the leaves are alternate with prickled edges and have variable shapes. Like dandelions, it contains a milky sap inside the stem. The yellow flowers develop from June to September in loose clusters at the end of the stems then produce up to 13,000 seeds with wings. This plant can reproduce by seed and creeping roots. It can be controlled by hand-pulling, repeated cultivation, mowing and/or herbicides.

Sulphur Cinquefoil (Potentilla recta) is a long-lived perennial that has been recently found in the Crowsnest Pass. It has a very similar native cinquefoil species but can be distinguished by noticeable perpendicular hairs on stem and leaves. Invasive Sulphur cinquefoil has pale yellow flowers with 5 deeply notched, rounded petals from June to July. It has 5 hairy sepals, palmately compound leaves with 5-7 toothed leaflets, it is important to note the underside of the leaf is green. Native cinquefoil species will have silver or different coloured underside. Sulphur cinquefoil has few basal leaves and many that grow along the stem. It will be 30-60 cm tall, and the stems will have perpendicular hairs. It has fibrous, woody roots and spreads up to 1400 seeds per season. This plant belongs to the rose family and the species name recta, means ‘erect’ or ‘upright’. Please report any sightings to Environmental Services Department.

Tall Buttercup (Ranunculus acris) is native to Europe and has an upright yellow flower that sits on a long-branched stalk with a waxy appearance. This weed flowers from June to September. Tall buttercup contains an irritating oil making it toxic to grazing animals, especially cattle. Tall buttercup can be controlled through cultivation, as the toxins dry up once the plant has been severed. Tall buttercup prefers moist to well drained humus soils, however with sufficient moisture, they can handle coarse soils as well. You will find them in pastures, ditches, aquatic areas, and forests. Tall buttercup has 5 yellow petals, 5 small green sepals and has leaves that are deeply divided into 3-5 segments. Knowing how to identify to the leaves of Tall buttercup can help you differentiate them from native species Yellow Avens (Geum aleppicum) and non-native and prohibited noxious Sulphur Cinquefoil (Potentilla recta). Control methods include herbicide, mowing or hand-pulling before seed set.

Yellow Toadflax (Linaria vulgaris) is a perennial, belongs to the Snapdragon family, native to Europe and is also known as butter-and-eggs or Common Toadflax! You can identify this plant by its yellow flowers from June to September, they are attached by short stalks and the lower lip has an orange, fuzzy spot. The flowers are arranged in a dense cluster, or terminal raceme. The leaves are very narrow, alternate arrangement, pointed at each end and attached directly to the stem without clasping. These plants can tolerate a wide range of growing conditions and have an extensive creeping root system. They can also reproduce up to 5,000 seeds per plant! Repeated hand pulling is an easy control method for these woody, rhizomatous roots that may grow several meters long, herbicides work as well. Before this plant has flowered it is often confused with leafy spurge, however, this plant lacks the milky latex when broken apart!

Canada Thistle (Cirsium arvense) is a perennial plant that made its way from Eurasia to Canada through contaminated crop seed. It develops a rosette in its first year then reproduces through deep, spreading roots and by dispersing seeds that can remain viable for 20 years. This plant belongs to the Sunflower family and produces a purple- pink flower from July to September which have bracts with no spines. The leaves are glossy, alternately arranged, spine-tipped and stalkless with wavy edges. The stems are erect with prickly spines and can be slightly hairy. The Canada thistle can grow up to 120 cm tall and is supported by creeping roots that can spread 4.5 m wide and 6 meters deep! This is the only thistle that has both male and female flowers. You can find Canada Thistle just about anywhere in the province of Alberta. They are drought resistant and thrive in a variety of soil types in disturbed areas, crop and pasturelands, grasslands, stream banks and urban areas. This weed is problematic because it outcompetes vegetation causing severe crop-yield losses, reduces access, and nesting cover for waterfowl.  Herbicide, mowing, or hand-cutting reduces infestations and can eventually exhaust root reserves and eliminate the plant.

Creeping Bellflower (Campanula rapunculoides) is a creeping perennial that was introduced as an ornamental from Europe. From June to August you can identify these plants by their purple-blue, bell-shape flowers that have 5 fused petals, 5 green sepals and nodding flowers. The leaves are alternatively arranged and have a wide range in leaf variability but will generally be heart shaped with jagged edges. Often confused with the native Bluebells, the Creeping Bellflower is usually much taller, upwards of 100 cm, has larger flowers and creeping roots.  The Creeping Bellflower is a common lawn weed and is difficult to eradicate because it can reproduce by seed and aggressive thick creeping rhizomes. These plants can produce up to 15,000 seeds per plant! The best control methods include hand-pulling, digging up as much root as possible, and smothering area with tarps or cardboard.

Dames Rocket (Hesperis matronalis) can be seen in the Crowsnest Pass from June to August with its vibrant magenta flowers. These weeds outcompete native vegetation quickly with their early spring growth and dense cluster formations. The leaves are lance-shaped, have toothed edges and have very small hairs on both sides. The rosettes feel like velvet. The stems reach 1 m tall and stabilize themselves with slender, shallow roots. The flowers have 4 petals that are borne in loose clusters at the top of the stems. These flowers produce long, thin seed pods that hold up to 20,000 tiny black seeds per plant. These weeds can be found in ditches, forests, aquatic and residential areas. The best control methods are repeated cutting before seed set or hand pulling the entire plant.

Himalayan Balsam (Impatiens glandulifera) is native to India and is also known as touch-me-not and policeman’s helmet. This is an annual plant introduced as an ornamental. The seed pods explode, spreading up to 4000 seeds, 10 m in diameter. Himalayan balsam is commonly found in riparian, disturbed, forest and urban areas. Himalayan balsam thrives in rich soils and has water buoyant seeds. From June to October, you can see its irregular flower. The flower has 5 petals and is purplish-pink, and sometimes white. The leaves are simple, oblong and have serrated edges. The leaves are arranged opposite on the stem, in whorls of three. The stems are 4-sided, hollow, and grow up to 120 cm. Himalayan balsam has shallow, fibrous roots so the best control method for this plant is hand-pulling/ digging the entire plant out.

Hound’s Tongue (Cynoglossum officinale) is found in pastures, roadsides, and waste areas. It was introduced from Europe and belongs to the Borage family. It has toxic properties that can cause animals to have liver failure if consumed. Hound’s tongue is a biennial plant that has small reddish-purple flowers that are funnel-shaped hanging in small clusters from leaf axils, June to August. Being a biennial plant, it produces a basal rosette in the first year and then flowers in the second year. The leaves are oblong, up to 30 cm long and are hairy on both surfaces. The seed pods are known as ‘hitchhiker’ seeds with their prickly, bur-like pods. This plant grows up to 1.5 m in height, have branches to the top and are covered with hairs. This plant is regionally common, and found in forests, pastures, and disturbed areas. The best control measures are hand-pulling/ digging the entire plant out, biocontrol, or destroying with herbicides.

Spotted Knapweed (Centaurea stoebe) is perennial plant native to Eurasia and belongs to the Sunflower family. These weeds have seed heads that persist until the following year and have distinct bracts that can be identified year-round with their dark, triangular fringed tips. Spotted knapweed has a grayish-green stem and leaves, and flowers from July to September. The flowers are pinkish-purple and develop on the end of the stem branch. This invasive plant is regulated as prohibited noxious because it exudes a chemical called catechin which prevents neighbouring plants from being able to germinate. It also has a deep taproot competing for food and water. This short-lived perennial can reproduce by seeds and root fragments that resprout, enabling it to outcompete native vegetation. Spotted knapweed prefers well drained, light textured soils in full sun. They can be found in disturbed areas, fields, roadsides, and other open areas. To destroy Spotted Knapweed, it is best to wear gloves and dig the entire plant out to avoid re-sprouting from taking place, or treat with herbicides. Removing the flowerheads will stop the plant from producing seeds and control the spread but will not destroy the plant.

Baby’s breath (Gypsophila paniculata) is a perennial plant native to Europe and belongs to the Carnation family. This invasive species is regionally common in Alberta and reproduces by seed. During the winter months, it breaks off and turns into tumbleweeds. The flowers are numerous, white, and small with 5 petals. A sweet scent and star-shaped appearance can be seen from June to September. The leaf arrangement is opposite and has a prominent mid-vein. The stems can grow up to 1 m tall with a root growing up to 4 m deep. One plant can produce and spread up to 14,000 seeds and it prefers to grow in riparian areas, pastures, grasslands, and urban areas. It has a native look-a-like species called Native pepper-grass (Lepidium spp). You can differentiate the two by number of petals on the flowers, native pepper-grass only has 4 petals. You can control this weed with herbicides, cultivation, or hand-pulling.

Black Henbane (Hyoscyamus niger) is a biennial weed flowering from July to September. When consumed this plant is poisonous to humans and livestock and should be removed carefully due to irritating hairs. Black henbane originated in the Mediterranean and belongs to the Nightshade family. The flowers are cream coloured with dark purple veins, has 5 lobes and are bell-shaped. There are usually a few flowers per stem which have a garbage-like odour. Black henbane produces a basal rosette the first year that has prominent white mid-vein, and the leaves are covered with hairs. The second year, this weed grows up to 1 m tall and the entire plant is covered with hairs. The seed capsules are extremely large, bell-shaped and are papery thin with triangular edges. The seed capsules are typically aligned on one side of the stem and leave a woody skeleton after seed set. One Black henbane plant can spread up to 500,000 seeds! This is a unique looking plant which makes it easier to identify! The best way to control these weeds is by hand-pulling, mowing, herbicides and cutting at the base of the plant and/or rosette.

Field Bindweed (Convolvulus arvensis) is also known as devil’s vine or wild morning glory. It is a perennial that is native to Africa, Asia, and Europe. When it comes to reproduction, it can spread by seeds and creeping roots. The flowers are funnel shaped, white to pinkish in colour and about 2.5 cm in diameter, seen from June to early September. The flowers bloom in the summer and close when it is dark, raining or overcast. The leaves are dark green, arrowhead shaped and are alternately arranged on the vine-like stem. These plants have a deep taproot with extensive creeping roots that are whitish in colour, fleshy and brittle. This plant produces 500 seeds per plant and are viable for up to 60 years!  Field Bindweed prefers disturbed areas, pastures, cultivated fields and roadsides. This plant is problematic because it will host viruses that affect crops like tomatoes and potatoes and is mildly toxic to livestock. Frequent hand pulling, cultivation or herbicides before seed set will help control this plant.

Garlic Mustard (Alliaria petiolata) is an extremely invasive biennial plant that has recently been found in the Crowsnest Pass and northern Alberta. It is critical that all possible sightings of this plant are reported to the Environmental Services Department. A basal rosette is produced in first stages of growth with a flowering stem in the second year and all parts of the plant smell like garlic when crushed. This plant can invade undisturbed forests, aquatic areas, and residential areas. You can identify this plant by its heart-to-spade shaped leaves that have toothed edges. The toothed edges will gradually get smaller as the leaves move up the erect stems. From April to July, these weeds have small 4-petaled flowers that are white with yellow centers, measuring 1-1.5 cm across. The flowers form clusters at the end of the stems. Stems typically have 1-2 branches per plant and they stand tall up to 1.5 m. This plant has a slender taproot with an s-bend, or crooked root just below soil level. The fruit pods are up to 6 cm long and contain 850 seeds per plant. Garlic mustard prefers rich, moist, forest soils and can tolerate full sun or dense shade. This plant reproduces by seed; hand-pulling is the best control method. There are currently no registered herbicides for this plant. Other names for this biennial plant include Poorman’s mustard, Garlicwort and Jack-by-the-Hedge garlic.

Hoary Cress (Lepidium draba) is a perennial plant from the Mustard family. There are three similar species listed under the Weed Control Act which can be differentiated by their seed pod shapes; globe podded, heart podded, and lens podded. These weeds have clusters of white flowers with 4 petals from April to July. Often referred to as Whitetop, the flowers form a flat-topped umbel appearance giving rise to the name. The leaves are blueish-green, alternate, and covered in soft, tiny hairs giving the leaves a felt texture. The leaves are lance to arrowhead shaped and the upper leaves clasp to the stem that grows up to 60 cm tall. Hoary cress has deep, extensive roots which is one of the ways these weeds reproduce. Hoary cress also spreads up to 3,500 seeds per plant. You can spot these invasive weeds in disturbed areas, grasslands, pastures, and residential areas but they require full sun with moderately moist to slightly dry soils. Mowing, cultivation, and herbicide are appropriate control methods.

Oxeye Daisy (Leucanthemum vulgare) is a perennial that belongs to the Sunflower family and is native to Europe. Oxeye daisies are unpalatable to cattle and will quickly displace native vegetation as they reproduce by seeds and creeping roots. In early spring they can be recognized by their dark-green, low-lying rosettes with spoon-shaped leaves. From early June to September, you can spot these daisies by their white petals and yellow centered flowers, often confused with noxious scentless chamomile. The flowers have 20-30 petals located at the branch ends. The lower leaves are spoon-shaped and arranged alternately on the stems. The lower leaves are lobed or have toothed edges and long leaf stalks whereas the upper leaves are narrow and clasped to the stem. These plants tolerate a wide range of conditions and can be found almost anywhere. The roots are short and fibrous , when hand pulling you want to make sure you dig the entire plant out, removing the creeping, fibrous roots, and rhizomes to avoid regeneration.

Scentless Chamomile (Tripleurospermum inodorum) was introduced from Europe and can be commonly seen on waste areas, roadsides, and cultivated fields during the months of June to September. The stems grow 20-100 cm tall, are hairless and odourless when crushed, living up to its name. The leaves have alternate arrangement, and the carrot-like leaves differentiate it from Oxeye Daisy. Scentless chamomile can produce over 300,000 seeds and remain dormant for several years. The stems are highly branched and can range from 5 cm to 100 cm tall. Scentless chamomile is a biennial or short-lived perennial that produces a basal rosette in it’s first year before turning into a reddish stemmed plant in it’s second year. This plant can handle a variety of conditions ranging from heavy clay soils, dry sites, and flooded areas. You can destroy this plant with herbicides, hand pulling the entire plant, or you can control it with biocontrol agents and/or removing flowerheads. There is a seed-head feeding weevil and a gall midge which have been used to help control this noxious species.

Wild Caraway (Carum carvi) also known as Common Caraway has been elevated to a noxious weed in the Crowsnest Pass. It is the property owner or occupiers’ responsibility to control this noxious plant and prevent further spread of its seeds. Wild Caraway is a biennial plant, growing a low-lying rosette the first year and grows a flowering stalk in it’s second year. The rosette can be confused with native yarrow or wild carrot because it has finely divided leaves that appear fern-like. The stems are usually glossy, grow up to 90 cm tall and are branched in the upper portion of the plant. The flowers form in umbel shaped clusters growing on long stalks. This weed flowers from May- August and the flowers have 5 heart-shaped petals that appear pale pink to white in colour. This plant is native to Eurasia and was brought to Canada for cultivation, it has since escaped and become established as an invasive species in some parts of Alberta. The seeds are evenly ribbed, 3 mm long which break into 2 single-seeded segments. Once seeds have been produced this plant is very delicate, if seeds are present, the best practice is to place a bag overtop of the plant and close tightly around the stem to avoid dropping any seeds. You can keep this plant under control by hand-pulling, repetitive cutting of flower stalk before seed set, or with herbicide applications.

This plant is native to Eurasia and was brought to Canada for cultivation. It has since escaped and become established as an invasive species in some parts of Alberta. You can keep this plant under control by repeated hand-pulling and cutting down the plant before seed set. The seeds are evenly ribbed, 3 mm long, and break into 2 single-seeded segments. This plant is very delicate once seeds have been produced so if seeds are present, the best practice is to place a bag over top of the plant and close tightly around the stem to avoid dropping any seeds. If you believe you have some rosettes growing in your yard or if you have seen any of these invasive plants in the Crowsnest Pass, please contact the Agriculture and Environmental Department through our reporting website Omnigo Software - Online Reporting Main 

Downy Brome (Bromus tectorum) also known as cheatgrass, can rapidly spread up to 5,000 seeds per plant. Downy brome is reddish-purple at maturity and the flowering spike droops to one side. The awns are 7-20 cm long, they are twisted and covered with soft hairs that can irritate the mouths of livestock and wildlife. Leaf blades are long and covered with soft hairs, when pulled back, there is a white, papery thin ligule 1-3mm long, helping you distinguish from other grasses. This plant has fibrous roots, and the plants height depends on availability of moisture. This plant is regionally common and can be found in disturbed areas, crops, pastures, and grasslands. Downy brome is a winter annual, native to the Mediterranean and belongs to the Poaceae family, also known as the grass family. Downy brome can be easily hand pulled.

Blueweed (Echium vulgare) is a biennial plant that belongs to the Boraginaceae family. In it’s first year it produces a basal rosette that radiates from the center point. Flowering stalks grow from the rosette producing flowers on the upper side of short, arching branches. The black taproot has some fibrous lateral roots and can be difficult to remove. Blueweed is unpalatable to grazers and is potentially poisonous due to toxic alkaloids. This invasive weed has numerous funnel shaped flowers often purplish-blue in colour seen June through September. Although rare, these flowers can also be pink or white. The entire plant is covered in bristly hairs that can cause skin irritation. Blueweed prefers growing in dry, rocky areas, gravelly riparian areas, roadside, pastures, and meadows at mid to low elevations. It requires well drained soils and does not tolerate shade very well. Blueweed is best controlled by digging out and removing the entire plant. Try to sever below the soil line, removing as much of the root as possible when the soil is moist. Repetitive mowing before seed production can help deplete root reserves. Do not place lawn trimmings in compost if they may contain blueweed seeds.

Orange Hawkweed (Pilosella aurantiaca) is often referred to as Devil’s paintbrush but shares little resemblance with native species Red Paintbrush. Orange hawkweed is a perennial plant belonging to the Sunflower family. On the end of each stem, it has red-orange dandelion-like flowers that can be seen from June to August, and sometimes through to September. The flowers are arranged in clusters and the bracts have coarse black hairs. Leaf edges could be smooth or slightly toothed with long hairs. The stems are erect growing up to 60 cm tall with few leaves. This weed can reproduce with fibrous, rhizomatic roots and mat-forming stolons. Orange hawkweed produces up to 1,500 seeds per plant. Hand pulling prior to flowering is a great control option but if flowers are present, is important to note that treatment of flowering plants can facilitate seed production and all plants must be bagged right away. Herbicide can be applied prior to flowering.