Description: Blueweed was introduced into North America from Africa as an ornamental and is now found across Canada and the United States. It has a large taproot and multiple lateral roots with a large flower spike that may reach to 80 cm.
Type: biennial forb
Habitat & Impacts: This species is found in a wide range of dry sites but prefers areas with dry, coarse soils, particularly those of limestone origin. Blueweed is not palatable and decreases quality of rangelands and pastures.
Method of Spread: Blueweed reproduces exclusively by seed. Seed production is moderate with up to 2,800 seeds produced per plant. Seeds can remain viable in the soil for several years. The seed may stick to clothing, hair or feathers.
Location: within City of Quesnel, as well as surrounding side roads. Major site at the Hanson gravel pit near Quesnel with scattered sites along highway 97 between Quesnel and Alexandria. Isolated sites exist in Churn Creek, Dog Creek, Gustafson Lake, and Bella Coola Valley. Prevalent south of the plan area in the Thompson Nicola Regional District.
Mechanical: Repeated cutting of blueweed plants prior to flowering can reduce seed production, but is less effective at killing older plants. Hand pulling can be effective on small infestations as the long taproot can be removed intact. Blueweed does not usually survive repeated cultivation.
Chemical: Several chemicals are recommended for Blueweed:
• 2,4-D can be applied in spring or early autumn for short-term control. Fall treatment is more effective than spring treatment.
• Glyphosate can be used for short-term control in non-vegetated areas. Glyphosate is not recommended for use in areas where desirable perennial vegetation occurs.
• Picloram provides long term, residual control.
• Clopyralid is effective at high rates and is recommended for use under or near conifers.
(Invasive Plant Council of BC, 2008)
Biological: There is no biocontrol currently available for blueweed.
CCCIPC Priority & Treatment Strategy: Priority 2 (containment) in North Cariboo, and Priority 1 (new invader) in the rest of the region. Blueweed is considered a priority invasive plant in the Cariboo Chilcotin Coast due to the serious implications for rangeland productivity in areas where it is well established. Blueweed occurrence is minimal in the Cariboo Chilcotin Coast, and continued control by management agencies will aid in preventing blueweed from becoming more widespread in the area.
Local Level - hand pulling small infestations
Landscape Level - chemical control for larger site
Invasive species profile taken from the Cariboo Chilcotin Coast Invasive Plant Committee Invasive Plant Regional Strategic Plan
Page last modified: March 15, 2017 09:36:29 PDT