Musk Thistle
Place of Origin: W. Asia, SE Europe and N. Africa
Place of Harm: All US except Florida, Canada, S. Africa, Australia
First Introduced: Early 1800’s, maybe 1852
Harms: native plants, livestock forage
Other Names: nodding thistle, nodding plumeless thistle
Musk thistle is a biennial herb (though sometimes a winter annual) most likely introduced accidentally through contaminated ballast water. It grows up to 6 ft tall and spreads by wind-dispersed seeds; each plant can produce up to 120,000. Seeds can stay viable for up to 10 years. Musk thistle has a long fleshy taproot. It lives in disturbed grasslands, pastures, grain fields, roadsides, and construction sites. It can be found in neutral to acidic soils, and prefers moist soil. The problem with musk thistle is that it crowds out native species. It also pushes out important forage crops that feed livestock (livestock do not eat musk thistle due to the spines). This makes it an especially dangerous pest in pastures because livestock will go only for the native grasses they eat, freeing up space and competition for musk thistle. Musk thistle can be controlled by pulling; this should be done before seeding to avoid spreading the seeds. Cut plants should be bagged and disposed. Livestock will eat plants after they are cut. The rosette weevil (Trichosirocalus horridus) and the thistlehead-feeding weevil (Rhinocyllus conicus; may reduce seed production by 50%) are biological controls currently released for control; however, the latter is troubling native plants and is being reconsidered. Also, herbicides like picloram or glyphosate can be applied; this is best done in the rosette stage (ASAP) or while flowering. Fall treatments should kill all rosettes; early spring treatments should prevent rosettes that sprouted later in the season from producing seed. Seedlings emerge in late July. The plants start out the first year in a low rosette stage, able to spread 4 ft wide. In mid-March of the second year they reach the bolt stage; stems quickly grow up and each plant produces up to 50 flowerheads from May to August; seeds are spread one month later by wind. The vast majority fall within 100 m of the parent. Seeds remain viable for over ten years. After seeds mature, the plants die. Musk thistles are edible to humans and are a nectar source for birds and bees. They are also used as a traditional medicine in India.
Place of Origin: W. Asia, SE Europe and N. Africa
Place of Harm: All US except Florida, Canada, S. Africa, Australia
First Introduced: Early 1800’s, maybe 1852
Harms: native plants, livestock forage
Other Names: nodding thistle, nodding plumeless thistle
Musk thistle is a biennial herb (though sometimes a winter annual) most likely introduced accidentally through contaminated ballast water. It grows up to 6 ft tall and spreads by wind-dispersed seeds; each plant can produce up to 120,000. Seeds can stay viable for up to 10 years. Musk thistle has a long fleshy taproot. It lives in disturbed grasslands, pastures, grain fields, roadsides, and construction sites. It can be found in neutral to acidic soils, and prefers moist soil. The problem with musk thistle is that it crowds out native species. It also pushes out important forage crops that feed livestock (livestock do not eat musk thistle due to the spines). This makes it an especially dangerous pest in pastures because livestock will go only for the native grasses they eat, freeing up space and competition for musk thistle. Musk thistle can be controlled by pulling; this should be done before seeding to avoid spreading the seeds. Cut plants should be bagged and disposed. Livestock will eat plants after they are cut. The rosette weevil (Trichosirocalus horridus) and the thistlehead-feeding weevil (Rhinocyllus conicus; may reduce seed production by 50%) are biological controls currently released for control; however, the latter is troubling native plants and is being reconsidered. Also, herbicides like picloram or glyphosate can be applied; this is best done in the rosette stage (ASAP) or while flowering. Fall treatments should kill all rosettes; early spring treatments should prevent rosettes that sprouted later in the season from producing seed. Seedlings emerge in late July. The plants start out the first year in a low rosette stage, able to spread 4 ft wide. In mid-March of the second year they reach the bolt stage; stems quickly grow up and each plant produces up to 50 flowerheads from May to August; seeds are spread one month later by wind. The vast majority fall within 100 m of the parent. Seeds remain viable for over ten years. After seeds mature, the plants die. Musk thistles are edible to humans and are a nectar source for birds and bees. They are also used as a traditional medicine in India.
Essential Question
"Could a genetically engineered invasive species potentially be used in warfare?"