Musk Thistle
Carduus nutans
Class C
Widespread in the state. Management decisions for these species should be determined at the local level, based on feasibility of control and level of infestation.
Children & Pets
This plant may pose a particular risk to unsupervised children and animals due to its toxicity or potential for injury.
Livestock Hazard
This plant presents a threat to the health and/or quality of livestock.
Local Ecosystems
This plant is detrimental to native ecosystems, negatively impacting the quality of forage for wildlife and reducing biodiversity in plant communities.
QUICK FACTS
- Primarily an issue in overgrazed lands and disturbed soil. As the stem is too spiny for livestock to eat, they will consume the surrounding vegetation, further encouraging thistle growth and spread.
- The presence of one Musk Thistle promotes the germination of nearby seeds, rapidly creating localized outbreaks.
- Can produce between a few thousand and more than 100,00 seeds. Even though the seeds have a pappus (the white, fuzzy hairs that help the seeds become airborne), the vast majority of seeds will fall within 50 inches of the parent plant.
1. Overview
Musk thistle is an invasive weed with a flair for the dramatic, flaunting its purple blooms while quietly plotting a takeover of any disturbed pasture it can find. Beneath the showy exterior lies a highly competitive plant capable of producing thousands of seeds and crowding out native species with surprising efficiency.
Musk Thistle is widespread in New Mexico and occurs in most counties. It takes 2 years to fully grow, spending its first year as a rosette (a series of large leaves arranged in a circular pattern at the base) and sprouting its large stem and flower in the second year. It is easy to distinguish this thistle by its large flower that will droop to the ground, and its leaves have no fuzzy hair. Grazing animals will avoid it because it is too spiky to eat, and overgrazing the land will suppress any competition it might have faced. Because most seeds won’t travel far from the plant, the result is a dense monoculture of this invasive plant. [2] [5]
History of Musk Thistle
The musk thistle’s native habitat is wide, ranging from western and central Europe, northwards to Scotland, and extending to Sicily, central Yugoslavia, Ukraine, western Siberia, Asia Minor, and North Africa. In its native land, its population was kept in check by natural disease and predators that were not present in North America. Musk thistle was introduced to the United States in the mid-1800s and was recorded multiple times along the East Coast by the late 1800s. In the early 20th century, it began to appear in the Midwest, and by the 1940s, it was considered a potential problem in North America. Today, Musk Thistle can be found across most of the US and southern Canada. [1][15]
2. ID Guide
What does it look like?
Musk Thistle is characterized by its large flowers (2 to 3 inches in diameter), their deep rose to violet color, and their tendency to droop toward the ground. The Stem can stand 3 to 8 feet tall with spines along it. The leaves have silvery margins and, unlike other Thistles, lack hair and fuzz on their surfaces. [2]
Having trouble identifying a weed?
Contact your local conservation district or county extension agent.
Key Features
- Plant: Like the Bull and Scotch Thistle, the Musk Thistle is a biennial plant, producing a rosette in the first year and sprouting its stem and flowers in the second. After producing seeds, the plant will die.
- Roots: Large, fleshy, corky taproot that is hollow near the surface. [3]
- Leaves: Dark green with a light green mid-rib and mostly white margins. The leaves should be hairless on top and bottom with spines along the edges. [3]
- Flowers: Around 2 to 3 inches in diameter, purple to deep rose, rarely white. Behind the flower, there are needle-like bracts that connect to the stem [3]
- Seeds: 1/8 to 3/16 inches long, shiny, striated, yellow-brown, with a hairlike plume. Each flower can produce up to 10,000 seeds, of which 33% are viable, yielding 3,600 seedlings. They can survive for more than a decade in the soil, and it can take 15 years to reduce the number of viable seeds to below 1%. [3]
Wolfgang Bacher, inaturalist.org
The flower head is 1.5-2 inches in diameter and 1–2 inches long, bell shaped, and at the ends of branches.
Bruce Ackley, The Ohio State University, Bugwood.org
In its first year, bull thistle is a basal rosette with dark green leaves up to 3 feet in diameter.
Bonnie Million, Bureau of Land Management, Bugwood.org
Bull thistle is a biennial, but can act as a perennial until it flowers, then dies quickly afterward
Ohio State Weed Lab , The Ohio State University, Bugwood.org
Stem leaves have cottony hairs near the stem and sometimes on the bottom side of the leaf.
Tony Bean, inaturalist.org
In the second year, it bolts with a winged and spiked stem about 2–6 feet tall.
Forest and Kim Starr, Starr Environmental, Bugwood.org
Seeds are less than 4 mm long, and attached to pappus for wind dispersal.
3. Infestation Basics
“The prickly habit of thistles needs no comment, and all animals, save the donkey, are afraid to approach such well-armed plants. The spines on this species are very strong, and the large, handsome, reddish-purple flowers expand from May to October.”
– Anne Pratt, 1899
Where and how does it grow, and how does it spread?
Musk Thistle grows best when the soil is damp and plenty of light is available. They spend 90% of its life as a rosette, staying near the ground until the stem bolts upward, flowers, produces seed, and dies. [3]
The Musk thistle spreads by water, wildlife, livestock, and human activity. While less than 1% of seeds are effectively transported by wind, it still poses a risk, as just one seed can start an infestation. [3]
Key takeaway: Musk Thistle can remain in the seed bank up to 15 years, so constant vigilance is needed after an infestation.
Why is it so invasive?
Musk Thistle produces many seeds, which can remain in the seed bank for up to 15 years. They are avoided by livestock, which will eat around them, creating the perfect environment for a continued infestation in overgrazed land.
Carduus nutans is a highly competitive invasive species capable of displacing substantial portions of native vegetation in pastures and other disturbed environments. Because musk thistle is unpalatable to both wildlife and livestock, grazing animals selectively avoid it and concentrate their foraging on more palatable native plants. This selective grazing accelerates the degradation of native meadows and grasslands. As surrounding vegetation is repeatedly consumed, musk thistle remains untouched, allowing it to grow vigorously, outcompeting native species, and becoming a significant pest in grazing systems. [12]
Under optimal environmental conditions, musk thistle can form extremely dense monospecific stands, with reported densities of approximately 60,000 individuals per acre. Such infestations are often characterized as self‑perpetuating due to their capacity to suppress and, in some cases, nearly eliminate co‑occurring vegetation. Emerging evidence further indicates that musk thistle may synthesize and release allelopathic secondary metabolites that inhibit germination and growth of neighboring plant species, thereby facilitating its own recruitment, persistence, and competitive dominance. [13]
Key takeaway: Musk Thistle, once established, can be extremely difficult to eradicate, as its seeds can remain in the soil for up to 15 years, and it is not as readily consumed by wildlife or livestock as native plants.
Common risk factors for invasion
- Soil disturbance/ Open spaces: Musk Thistle seedlings require open spaces with adequate sunlight in order to become established in an area. As most seeds will only fall 50 inches from the parent plant, ensuring healthy competition should delay their spread. [3]
- Moisture availability: Musk Thistle needs somewhat moist soil to become established and seems to prefer abundant spring moisture; it has been shown that it can reach flowering stages with as little as 10 inches of annual rainfall. [1]
- Overgrazing: As livestock avoid eating the Musk Thistle, they will eliminate any competition that the Musk Thistle could have faced, and if allowed to overgraze, will provide conditions for a continued infestation.
Impacts
Ecosystem Health
Areas that are overgrazed could promote a Musk Thistle infestation, but the seedlings appear to be sensitive to competition, especially when it reduces light availability. [3]
Health and Safety
The edges of the leaves and the stem have needles, which can be painful if handled with bare hands. There are no known toxins in musk thistle, but it is frequently sprayed with herbicides to control its population. [11]
Economic
Areas that are overgrazed could promote a Musk Thistle infestation, but the seedlings appear to be sensitive to competition, especially when it reduces light availability. [3]
Agriculture and Food Security
While livestock can feed on the flowers, the stems and leaves are too thorny to consume and tend to be avoided when grown. In fact, livestock will avoid areas near the plants, resulting in reduced grazing capacity. [6]
4. Management Strategies
Effective management of Musk Thistle requires persistent effort, as the seeds can remain in the soil for up to a decade, and it can take 15 years to eliminate them. They only spread through seeds, so as long as the plants are removed before the flowers come out, there will be a positive impact on their population. [3]
They favor a wet ground in a poor vegetative state and respond positively to soils with an excess of nitrogen. Musk thistle seedlings’ growth directly correlates to the amount of light they receive, so an effective control method is to prevent sunlight from reaching them by ensuring competition from native perennial grasses and not letting overgrazing remove their competition. [3]
There are insects called the Head weevil and, to a lesser extent, the Rosette weevil that target the Musk Thistle; they were released in the 60s to combat the plant. However, due to the risk they posed to native thistles, it is now illegal to release them, and they no longer seem to be available for sale. They can still be found in nature and were seen in Taos County, NM as recently as 2023. [8][9][10]
DO’s
- Severing the plants from the roots will kill them, as new growth can only come from seeds.
- Remove the plants before they have the chance to produce seeds.
- Plant perennial grasses that can outcompete the thistle.
DON’Ts
- Avoid having any large amount of land that is both moist and devoid of local perennial grasses
- Don’t use fire! It can create favorable conditions for the Thistle to return.
- Don’t mow during or after flowering to prevent seed dispersal.
** The following information is provided courtesy of the UC Weed Research and Information Center. nmweeds.taosswcd-nm.gov does not endorse the use of any particular product, brand, or application thereof. **
Non‑chemical management of musk thistle relies on interrupting its seed cycle and strengthening competition from perennial grasses.
These thistles can be cultivated or manually removed when small. To control by cutting, use a sharpened shovel at the top of the root crown. Grubbing hoes must cut the plants 2 to 4 inches below ground level to prevent resprouting from dormant axillary buds. Mowing the plant during flowering can greatly reduce seed production, though a single mowing is seldom sufficient due to the wide differences in the maturity of plants in a natural population. For mowing, wait till plants bolt and are about to flower. This may require repeated visits at weekly intervals over the 4 to 7 week blooming period, because not all plants bloom simultaneously. Plants will regrow if mowed before they are fully bolted. Plants cut 4 days after the first flowers open can produce viable seed.
The ability of thistles to invade pastures can be changed by grazing management, primarily by changing the competitiveness of the desirable pasture species. Sheep, goats, and horses, but not cattle, will eat young plants and can have a significant effect on thistles in the early stages of an infestation.
It is unclear whether fire will completely kill bull thistle. Only mature thistle plants may readily combust and their seed may already be dispersed. Fire can create conditions that favor the establishment of bull thistle, so colonization after a fire may be enhanced.
The bull thistle gall fly (Urophora stylata) was released as a biocontrol agent in the Pacific Northwest, as was the thistle head weevil, Rhinocyllus conicus. R. conicus is widely established in the western United States and attacks many thistle species, including some native species.
The following specific use information is based on published papers and reports by researchers and land managers. Other trade names may be available, and other compounds also are labeled for this weed. Directions for use may vary between brands; see label before use. Herbicides are listed by mode of action and then alphabetically. The order of herbicide listing is not reflective of the order of efficacy or preference.
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2,4-D Several names |
Rate: 1.6 to 2.1 qt product/acre (1.5 to 2 lb a.e./acre) Timing: Postemergence at rosette stage. Treat seedling rosettes in fall. Remarks: 2,4-D is broadleaf-selective and has no soil activity. It may require repeat applications. 2,4-D is generally not the most effective treatment, but is widely used because of low cost. Use a surfactant. When using the ester formulation do not apply when outside temperatures exceed 80°F. |
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Aminocyclopyrachlor + chlorsulfuron Perspective |
Rate: 4.75 to 8 oz product (Perspective)/acre Timing: Postemergence and preemergence. Postemergence applications are most effective when applied to plants from the seedling to the bolting stage. Remarks: Perspective provides broad-spectrum control of many broadleaf species. Although generally safe to grasses, it may suppress or injure certain annual and perennial grass species. Do not treat in the root zone of desirable trees and shrubs. Do not apply more than 11 oz product/acre per year. At this high rate, cool-season grasses will be damaged, including bluebunch wheatgrass. Not yet labeled for grazing lands. Add an adjuvant to the spray solution. This product is not approved for use in California and some counties of Colorado (San Luis Valley). |
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Aminopyralid Milestone |
Rate: 3 to 5 oz product/acre (0.75 to 1.25 oz a.e./acre) Timing: Postemergence in spring to early summer when the target plants are in the rosette to bolting stage, or in fall to seedlings. Remarks: Aminopyralid is a broadleaf herbicide similar to picloram, but more selective and generally safe on grasses. Its soil residual activity will kill emerging seedlings. Aminopyralid has a longer soil residual and higher activity than clopyralid. Aminopyralid can also be used in a premix with 2,4-D (Forefront HL) at 1.2 to 1.5 pt product/acre for bull thistle control. |
|
Clopyralid Transline |
Rate: 0.67 to 1.33 pt product/acre (4 to 8 oz a.e./acre) Timing: Postemergence in spring up to the bud stage. Can also apply to fall regrowth. Results are best if applied to rapidly growing weeds. Remarks: Clopyralid is a broadleaf herbicide like picloram, but more selective. It is very safe on grasses. |
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Dicamba Banvel, Clarity |
Rate: 1 to 2 pt product/acre (0.5 to 1 lb a.e./acre) Timing: Postemergence to rosettes in spring. Fall applications help control seedling rosettes. Remarks: Dicamba is a broadleaf-selective herbicide often combined with other active ingredients. It is also effective when tank-mixed with 2,4-D (0.75 lb a.e./acre of dicamba + 0.25 lb a.e./acre of 2,4-D). Avoid drift to sensitive crops. Do not apply when outside temperatures exceed 80°F. Dicamba is available mixed with diflufenzopyr in a formulation called Overdrive. This has been reported to be effective on bull thistle. Diflufenzopyr is an auxin transport inhibitor which causes dicamba to accumulate in shoot and root meristems, increasing its activity. Overdrive is applied postemergence at 4 to 8 oz product/acre on rapidly growing plants. Higher rates should be used on large annuals and biennials. Add a non-ionic surfactant to the treatment solution at 0.25% v/v or a methylated seed oil at 1% v/v solution. |
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Picloram Tordon 22K |
Rate: 0.5 to 0.75 pt product/acre (2 to 3 oz a.e./acre) Timing: Postemergence during active growth before bud stage. Remarks: Picloram is one of the most effective herbicides for bull thistle control. Most broadleaf plants are susceptible, but relatively safe on established grasses. It is also effective when mixed with dicamba or 2,4-D. Picloram has long soil residual activity and has been reported by some to injure young or germinating grasses. Picloram can also be used in a premix with 2,4-D (Grazon P+D) to give control of bull thistle. Picloram products are federally restricted use pesticides. Picloram and its formulations are not registered for use in California. |
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Triclopyr Garlon 3A, Garlon 4 Ultra
|
Rate: 0.33 to 1.5 gallons Garlon 3A/acre or 0.25 to 1 gallons Garlon 4 Ultra/acre (1 to 4.5 lb a.e./acre) Timing: Postemergence to rapidly growing weeds, up to bud stage. Remarks: Triclopyr is broadleaf-selective and safe on most grasses. It is most effective on smaller plants. Garlon 4 Ultra is formulated as a low volatile ester. However, in warm temperatures, spraying onto hard surfaces such as rocks or pavement can increase the risk of volatilization and off-target damage. Recommended rates are based on those reported for perennial thistles. Triclopyr can also be used in a premix with 2,4-D (Crossbow) or clopyralid (Transline). |
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Chlorsulfuron Telar |
Rate: 1 oz product/acre (0.75 oz a.i./acre) Timing: Postemergence to young rapidly growing weeds. Remarks: Chlorsulfuron provides residual control 1 year after treatment. It has mixed selectivity, but is generally safe on grasses. Always use a surfactant. 2,4-D at 1 to 2 pt product/acre can be tank-mixed with chlorsulfuron for quicker burndown. |
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Imazapyr Arsenal, Habitat, Stalker, Chopper, Polaris |
Rate: Broadcast treatment: 4 to 6 pt product/acre (1 to 1.5 lb a.e./acre). Spot treatment: 1% v/v solution Timing: Postemergence at flowering. Remarks: Imazapyr is best used as a spot treatment. It is a nonselective herbicide. It also has long soil residual activity and can leave more bare ground than other treatments, even a year after application. Recommended rates are based on those reported for perennial thistles. |
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Metsulfuron Escort
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Rate: 1.5 to 2 oz product/acre (0.9 to 1.2 oz a.i./acre) Timing: Postemergence to young, rapidly growing weeds in spring before flowering, or in fall to new rosettes. Remarks: Metsulfuron has mixed selectivity, but is generally safe on grasses. Use a surfactant. It can be tank-mixed with 2,4-D or aminopyralid. Opensight is a premix of aminopyralid and metsulfuron; use at 1 to 2.5 oz product/acre. Metsulfuron has some soil residual activity. Recommended rates are based on those reported for perennial thistles. Metsulfuron and its formulations are not registered for use in California. |
5. Citations
[1] “Bull Thistle,” in The Weed Workers’ Handbook , Watershed Project and the California Invasive Plant Council. Available: https://www.cal-ipc.org/docs/ip/management/wwh/pdf/19637.pdf
[2] Washington State Noxious Weed Control Board, “Bull Thistle,” Wa.gov, 2022. Available: https://www.nwcb.wa.gov/weeds/bull-thistle
[3] Native Plant Society of New Mexico, “Bull Thistle,” Wildflowers of New Mexico. Available: https://npsnm.org/wildflowersnm/Cirsium_vulgare.html. Accessed: Jul. 17, 2025
[4] CABI, “Cirsium vulgare (spear thistle),” CABI Compendium, 2021. doi: https://doi.org/10.1079/cabicompendium.13631
[5] M. Alfs, “An Herbal Breakthrough in Rheumatology Bull Thistle (Cirsium vulgare) for Spondyloarthropathy,” Journal of the American Herbalists Guild , vol. 12, no. 3, 2014.
[6] “Bull Thistle – Cirsium vulgare,” Montana Plant Life. Available: https://montana.plant-life.org/cgi-bin/species03.cgi?Asteraceae_Cirsiumvulgare. [Accessed: Jul. 17, 2025]
[7] K., Zouhar. 2002. Cirsium vulgare. In: Fire Effects Information System,. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory. Available: https://www.fs.usda.gov/database/feis/plants/forb/cirvul/all.html
Bruce Ackley, The Ohio State University, Bugwood.org
The roots of bull thistle are edible and can be cooked to taste like Jerusalem artichoke. Young flower stems and leaves can be eaten cooked with other vegetables as well, but spikes must be removed from stem and leaf in order to eat, unless soaked with salt overnight. Flower buds and seeds can be eaten roasted. Bull thistle has little nutritional value, but was traditionally stored and eaten in colder months. [5]
Pavel Gorbunov, inaturalist.org
Rob Routledge, Sault College, Bugwood.org
Bull thistle has several medicinal uses, including joint pain relief. The roots can be used to make a paste for joint pain. The whole plant can be boiled and used as a steam for rheumatic joints or decoction for joint pain and bleeding piles. [5,6]
Rob Routledge, Sault College, Bugwood.org
Bruce Ackley, The Ohio State University, Bugwood.org
While most grazing animals avoid bull thistle because of its spikes, animals and insects like birds, grizzly bears, gophers, and pollinators enjoy eating various parts of this plant. This usually helps in preventing seed dispersal, but not killing existing mature plants. [7]
Rob Routledge, Sault College, Bugwood.org
Rob Routledge, Sault College, Bugwood.org
Barry Rice, sarracenia.com, Bugwood.org
John M. Randall, The Nature Conservancy, Bugwood.org
Eric Coombs, Oregon Department of Agriculture, Bugwood.org
Ohio State Weed Lab , The Ohio State University, Bugwood.org