Binomial Name: (Cirsium arvense)
Canada Thistle is a perennial angiosperm in the family “Asteraceae”, that belongs to Genus “Cirsium”. It's an aggressive grower and included in the lists of USDA invasive plants list that spread through its extensive root system outcompeting the instinctive plants. Due to a rapid colonization behavior, Canada Thistle threatens the ecosystem of rare and pervasive plant species. So the weed is considered a good element of change in the biodiversity of the habitats where it grows. However, it provides excellent nectar sourcing for the pollinators and may cause minor injuries to the livestock.
Origin and Distribution in the US
Canada Thistle has its ancestries in Eastern Mediterranean and Southeastern Europe, and it was brought to North America by cereals trade as a contaminant. Canada Thistle is a C3 Type Carbon fixation weed that successfully thrives in areas with abundant moisture, moderate temperature, and moderate sunlight since it depends on its spreading root system to absorb moisture and nutrients. It can be found extensively growing in a variety of habitats and the most favorable sites are freshly cleared lands, newly planted lawns, and the areas where human interaction is limited. It also infests disturbed and unattended habitats such as pastures, forests, landscapes, and roadsides for its speedy establishing features. Additionally, it poses possible threats to turfgrasses and orchards if good maintenance is lacking. Moreover, Canada Thistle hosts a variety of pests such as aphids, whiteflies, and leafhoppers.
Identifying Canada Thistle
Canada thistle is a thorny herb that can reach between 2-5 feet high. Its creeping roots can reach deep into the soil making clones, and each of these clones can grow into a new plant. The leaves are usually lobed having spiny teeth. Shallow ridges can be noticed on a smooth stem, while plant branches near the top. The flowers are showy white and pink. The Fruit or seeds are small dry tan with feathery structures that can disperse in the wind. Only a female Thistle plant produces seeds.
Lifecycle and Growth Pattern
Canada Thistle may sometimes extend roots up to 6 feet deep into the soil. These roots extend creeping rhizomes, and an individual rhizome can give rise to a new plant. Additionally, the lateral roots also behave similarly that could creep up to 12 feet near the soil surface giving rise to new plants wherever they anchor themselves. Both male and female clones flowering starts in the mid-summer that continues to early fall. Flowers pollination occurs through insects and birds whereas, the seeds disburse by the wind which, helps them colonizing Canada Thistle a new area rapidly. The seed germinates on getting favorable conditions and could remain dormant for up to 20 years in the soil. Canada Thistle becomes stress-free to identify once it produces flowers and fruits. Moreover, its compact clones and smooth stem differentiates it from other Thistle species growing in your lawn.
Fun Facts About Canada Thistle
Canada Thistle-Prevention & Control
Cultural Control
Canada Thistle is notoriously famous for the speedy growth of lateral roots and highly dispersible seeds which, are also abundantly produced. Our prime focus is to stop its seed production and the migratory seeds that could arrive from the neighborhood or a plants sourcing nursery. A three-way prevention and control strategy that involves manual, chemical, and mechanical methods could probably help in decreasing and abolishing seed banks that promote new growth. Hand-pulling them is practicable if a small population occurs in a landscape or a turfgrass but, clearing the heavy infestation could become a tedious job. Mowing is practicable on larger areas once Canada Thistle Plants produce buds and then before the flower set. If flower initiation takes place, seed disbursement is not stoppable. Moreover, adjusting the Mowing height close to the surface of turf would greatly help.
Organic Control
Weed Crush-Organic herbicide
Weed Crush is a non-selective organic herbicide that contains 15% Sodium Laurel Sulfate, a foaming agent that stops photosynthesis in the leaves, and they're killed on immediate contact if sprayed during the hours of sunshine. Otherwise, it takes 48 hours for the complete hold but, be assured that it kills everything that comes into its contact. Try to avoid established turfgrasses and use only on Orchards and vegetable beds. The targeted weeds are not only killed. But, also delay their regrowth.
- Quickly Burns Surface Weeds: This weed control spray kills on contact the toughest and most unsightly weeds that infiltrate your lawn, driveway, walkways, and other unwanted areas.
- Fast Acting, Long-Lasting Formula: With this weed burner, you'll see that unsightly vegetation shrivel up in as little as 15 minutes in optimal conditions. Kills them fully dead in 24 to 48 hours. Best if used on weeds under 12 inches.
- Inhibits Regrowth, Too: In addition to burning visible weeds, our weed preventer helps stop them from growing back and spreading. It's also rainproof and settles within just 30 minutes.
Weed Crush is available in ready-to-use concentrations where the gardeners need to connect only a garden hose to apply it on target weeds including, Canada Thistle and other broadleaf weeds.
Chemical Control
Control using Pre-Emergent Herbicide
Glyphosate 4 + Plus Herbicide
A pre-emergent herbicide required to stop the spread of Canada Thistle for general cultivation and during the preparation of lawns before planting is Glyphosate. It's a non-selective herbicide that kills all sorts of vegetation that comes into its direct contact. It is, therefore, recommended to apply Glyphosate at least one week before planting turfgrass in your lawn.
- Glyhosate 41%
- Glyphosate Plus 41% Glyphosate may be used in any area of vegetation. Care should be taken to ensure that non-target vegetation is protected from drift.
- For general application mix Glyphosate 4+ at a rate of 2 ounces per gallon of water and treat unwanted vegetation.
Add only 2-ounces of product concentrate in 1-gallon of water to apply to the targeted area.
Additionally, it contains a surfactant that sticks the liquid to the surface of the leaves for rapid and prolonged control if any vegetative growth is there.
Control using Post-Emergent Herbicide
Weedmaster
Weedmaster contains Dimethylamine salt of Dicamba and 2,4-D. Both of these active ingredients get absorbed by plants' foliage and roots, translocate throughout the plant parts and deposit at the points of growth. Both of these ingredients obstruct auxins, and weeds die eventually. The best for applying Weedmaster starts when the weeds and especially Canada Thistle is in the 5-7 leaves stage before flowering.
Add 1 ounce of Weedmaster in 1-gallon of water to spray on Canada Thistle and other broadleaf weeds.
For Turfgrasses, application rates vary between 2-5 pints per acre depending on the growth stage of Canada Thistle.
Spurge Power
Awesome chemistry that mixes MCPA, Dicamba, and Triclopyr acid in Spurge Power in the ratio of 56.14%, 3.60%, and 5%, respectively, provides excellent control over Canada Thistle and many other broadleaf weeds. The mode of action is both through roots and foliage penetration. Spurge Power is applicable on both summer and winter weeds and performs well when applied at a temperature below 70°F.
- EFFECTIVE BROADLEAF WEED CONTROL - Effective broadleaf weed control for hard to control weeds.
- CONTROL - Spurge Power contains 3 active ingredients that control Spurge, Dandelion, Oxalis, Creeping Charlie, Clover, Wild Violet, and other broadleaf weeds in lawn areas.
- FOR WARM AND COOL SEASON LAWNS - May be used on both warm and cool season lawns such as bluegrass, fescue, ryegrass, bentgrass, bahiagrass, bermuda grass, and zoysia.
Add one ounce of Spurge Power in 2 gallons of water and spray on Canada Thistle using a Knapsack or power sprayer.
Learn How to control and get rid of other weeds in our complete Yard Weeding Guide.