Weed Wednesdays

Annual plants complete their life cycle in one year meaning they go from germination, to flowering stalk to seed all in on year. There are two types of annuals: winter and summer annuals. 

Winter annuals live their life cycle throughout the winter; germinating in the fall, wintering over as a rosette then produce seed in the spring. They die back in late spring/ early summer completing their life cycle before summer. Good examples of this are Downy brome and Jointed goatgrass. Summer annuals, like Himalayan balsam, germinate in the spring and complete its life cycle by the end of the summer. The recommended time to control winter annuals is in the fall from mid-October to freeze up. Winter annuals can be controlled in the spring as well, but it is best to do early before these plants begin actively growing and green- up. 

For any further information on plant life cycles, you can contact the Agricultural and Environmental Department or stay tuned for more Weed Wednesday posts! 

Biennial plants live for two growing seasons. Their first year they produce a basal rosette and then in the second year they grow into a flowering stalk producing seeds. These biennials die back in the fall and do not return the following year. A basal rosette is a circle of leaves that lay close to the ground and radiate from the center point, typically the taproot. The fall is a great time to control these biennial plants while they are in the rosette stage.  

Examples of biennial weeds are common mullein, black henbane and blueweed. For any further information on plant life cycles, you can contact the Agricultural and Environmental Department or stay tuned for more Weed Wednesday posts! 

Perennials are plants that live more than three years and continue to come back year after. Some perennials can have substantial life spans; trees are a good example. Perennials typically have vegetative reproduction structures that enable them to reproduce without seeds. These can include stolons, rhizomes, bulbs, or tubers. There are two types of perennial plants: simple and creeping perennials.

Simple perennials grow as individual plants and have tap roots. They may regenerate after being cut or injured but typically reproduce by seed. The creeping rooted perennials have many horizontal creeping stems, such as rhizomes and stolons, that radiate out from the parent plant allowing it to generate tubers and/or new plant shoots.

An example of a simple perennial weed is baby’s breath, and examples of creeping perennial weeds are Canada thistle and Creeping bellflower. Perennials are best controlled when they are still growing in early fall, generally before harvest time. For further information on plant life cycles, contact the Agricultural and Environmental Department.

Common Burdock (Arctium minus) was the inspiration for Velcro by George de Mestral in the 1940’s. It’s prickly seed heads spread by sticking to anyone or any animal that brushes up against it. These burrs may be great for inspiring Velcro but are an issue for small birds and bats when they become entangled. These burrs are not only difficult to deal with for small animals but also for horses, sheep, and dogs when the burrs become trapped in their manes and fur. Common burdock has large leaves that prevent sunlight and water to reach other plants. It is a biennial plant in the sunflower family, native to Eurasia and if often found in areas where the soil has not been disturbed. It prefers pastures, barnyards, fence rows, stream banks, forest open areas, edges, and understories. Seed production begins in July and continues in the autumn spreading up to 16,000 seeds per plant. From June to August, Common Burdock produces pinkish-purple disc florets with lance-shaped bracts with hooked tips. Often confused with Great Burdock and Woolly burdock, it can be differentiated by the size of the flowers and burrs, although, all three of these burdock species are regulated as noxious weeds in Alberta. You can destroy this plant with herbicides, hand-pulling, or digging. Removal of flowerheads will control the spread.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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!