Weeds

Canada Thistle

Canada Thistle is a very aggressive noxious weed. It is extremely hardy and difficult to get rid of, leading to many County residents having this invasive weed in their backyards and fields.

• Aggressive perennial species, which is extremely hardy and spreads by both seed and roots/rhizomes.
• This weed populates aggressively on overgrazed pastures, poorly established areas, and drought conditions.
• A new plant can grow from just a small root fragment.
• The best control method is an integrated management approach.

Spray a selective residual herbicide registered for the control of Canada thistle, the best time for herbicide applications is at the early bud stage or early fall. Establish a healthy vegetative stand that will complete against Canada thistle, leaving it less able to germinate. Continuous Mowing is another options but is found less effective and more work, the mowing needs to be repeated every 21 days or less.

Canada Thistle Fact Sheet

Common Tansy

Common Tansy is a noxious weed which was introduced from Europe in the late 1600s for ornamental and medicinal uses. It has a very distinct smell and is toxic to most livestock.

Its fern-like appearance with a strong minty smell and yellow button shaped flower.

Perennial which spreads by seed and rhizomes (underground lateral roots)

Spray with a selective residual herbicide labelled for the control of Common Tansy. The optimum time to spray is earlier in the growing season while it is in a soft vegetative state before the plant goes to seed and the stem becomes hard and woody. If the plant has gone to seed manually dead- head and spray the leaves and stem. If it's a small infestation dig out with a shovel, bag and sent to your nearest landfill.

Common Tansy Fact Sheet

Field Scabious

Field Scabious is a noxious weed which originates from Europe. It is very aggressive and tends to displace all other vegetation in pastures and forage stands.

This is a highly invasive perennial which was introduced to North America as an ornamental plant. Once established is difficult to eradicate, requiring persistent and diligent control work. Control options are to use a selective registered herbicide labelled for the control of Field Scabious, mowing can be beneficial to remove seed production, but will require consistent mowing and/or hand pulling.

Field Scabious Fact Sheet

Leafy Spurge

Leafy Spurge is an aggressive noxious weed that tends to displace all other vegetation in pastures and rangeland. As this plant is poisonous to most livestock with the exception of sheep and goats, livestock will not ingest it unless food is scarce.

Leafy Spurge is a long lived perennial that re-sprouts from an extensive and persistent root system. Their roots can extend 4.5m laterally and 9m deep. Key identifying feature of Leafy Spurge is that all parts of this plant contain a milky-colored latex in the stems and leaves. Control is herbicide application with a selective registered herbicide for the control of Leafy Spurge, as well as an intensive mowing or cultivation program.

Leafy Spurge Fact Sheet

Perennial Sow Thistle

Perennial Sow Thistle is an aggressive, creeping weed that can severely reduce yields in cultivated fields. It has adapted to a wide range of environmental conditions. There are a wide range of registered herbicides which control PST. Mowing, cultivation into annual crop, and hand pulling are all viable control options.

Perennial Sow Thistle Fact Sheet

Tall Buttercup

Tall Buttercup, also known as Common Buttercup, is a noxious weed native to Europe. It contains a bitter juice, which causes blistering of the mouth and digestive system when consumed by livestock.

This perennial weed only spreads by seed. Tall buttercup contains a bitter and irritating oil in the stem called protoanemonin. This weed is very common in wet areas of pastures. Use a registered herbicide for control or mowing during early bloom followed by continuous mowing every 21 days.

Tall Buttercup Fact Sheet

White Cockle

White Cockle is a noxious weed which is native to Europe. It prefers full sun and rich, well-drained soils, and can be common in hay fields and difficult to control with alfalfa and clovers. Frequent mowing will reduce seed production as well as herbicide control with a registered control of White cockle.

 White Cockle Fact Sheet

Yellow Toadflax

Yellow Toadflax is a noxious weed which is native to Europe and introduced to North America. This plant prefers well-drained sandy or gravelly soils, dry summers, and open, sparsely vegetated sites. These weeds contain a poisonous glycoside that may be harmful to livestock.

Yellow Toadflax resembles a snapdragon (bright yellow with orange throat). This is a perennial that spreads by roots and seed. It flowers June – autumn. A new plant can grow from a fragment of root, cultivation is not a viable option. It is better to control by registered herbicide or very frequent mowing to spot seed production, but this is not ideal.

Yellow Toadflax Fact Sheet

Scentless Chamomile

Scentless Chamomile are usually very bushy and have a fibrous root system, with a daisy like flower. It continually blooms, forms seed, and seeds germinate throughout the growing season: fall seedlings overwinter and are usually first to flower in spring. Native to Europe, it was introduced as an ornamental and/or a contaminant in crop seed. Control options are to spray before it flowers with a selective residual herbicide for the control of Scentless Chamomile. If this plant is sprayed after flower, the seed is still viable. The second control option is to pick, bag and take to your nearest landfill.

Scentless Chamomile Fact Sheet

Sea Buckthorn

In September 2019, Lacombe County Council passed Bylaw 1299/19, which elevated Sea Buckthorn to a local Noxious Weed within Lacombe County.

Originating from Eurasia, Sea Buckthorn is not a native species to North America. It is highly invasive (especially in riparian areas) and displaces naturally occurring vegetation and wildlife. Due to its thorny branches, Sea Buckthorn creates a barrier that divides and prevents access to Gull Lake through infested areas.

Plant Description

• Dense and stiff branches, that are very thorny.
• Leaves are a distinct pale silvery-green, lanceolate, 3–8 cm long, and 7 mm broad.
• Roots distribute rapidly and extensively through rhizomes and through seed dispersal.
• Berries are an attractive food source for wildlife.
• Male plants produce brownish flowers, which wind distribute pollen.
• Females produce fruit, and seeds, and have flowers without petals.

Facts

• Sea Buckthorn is often used as an orchard species.
• The berries can be harvested by hand but present a challenge due to the thorniness of the branches.
• The fruit is strongly attached and is not easily stripped from the dense shrub.
• As an allelopathic plant, Sea Buckthorn releases growth inhibitors into the soil preventing the establishment of native plant species.

Control Methods

• Mowing can slow the growth of Sea Buckthorn but won't eliminate it.
• The entire root system needs to be dug out/excavated, to stop it from re-establishing itself.
• Treat regrowth with an appropriate herbicide.

Himalayan Balsam

Himalayan balsam is a summer annual of riparian areas which is produced by seed only. Seeds germinate in spring to produce dense, even-aged stands which shade-out competing vegetation. Growing up to two meters tall, has shallow fibrous roots that make it easy to hand pick. Prevention is key with HB, most infestations start by ornamental plantings and can be spread by water or soil.

Himalayan Balsam Fact Sheet

Spotted Knapweed

Primarily a biennial plant – producing a rosette the first year and a flowering bolt the second – but can also be a short-lived perennial, blooming for a few years before dying.

Spotted knapweed can self-pollinate and is also cross-pollinated by insects. A prolific seed producer – individual plants can produce over 140,000 per year – control is extremely difficult on established infestations.

Spotted Knapweed Fact Sheet