Scotch Thistle

Biological Name:

Onopordum acanthium (Scotch-Thistle)

Natural Habitat:

Scotch-Thistle: Grassy areas, Europe


Scotch-Thistle also known as Onopordum is a plant that is native to grassland and prairie regions of North America. It is a biennial or short-lived perennial that can grow up to six feet tall and it has large spiny leaves and showy purple flowers that bloom in the summer. The plant is known for its sharp spines which can cause injury to humans and animals and it is considered to be a noxious weed in many areas.

Frequently Asked Questions (FAQs)

Q: What is Scotch thistle good for?
A: The biennial plant of the family Asteraceae, Onopordum acanthium L., also known as Scotch thistle, is used in traditional medicine as an anti-inflammatory, antitumor, and cardiotonic agent.

Q: Is thistle good for your liver?
A: Most studies show milk thistle improves liver function and increases survival in people with cirrhosis or chronic hepatitis.

Q: Can you eat Scotch thistles?
A: The stems can be peeled and then steamed or boiled. I loved them raw, harvesting the stalk of the advanced plants before they go to flower. The tap roots can be eaten raw or cooked, also of young thistles that have not flowered yet. The dried flowers are a rennet substitute for curdling milk.

Q: Is thistle poisonous to humans?
A: Health Risks: Entire plant is highly toxic to humans and livestock, causing vomiting, diarrhea, respiratory issues, and spasms.

Q: Why is thistle a problem?
A: They have become major problems in agricultural landscapes and 22 states have designated them as noxious weeds. Thistles do attract pollinators and birds, but the spiny leaves and stems keep grazers away. Some thistles release chemicals into the soil that inhibit the growth of other plants.

Q: Can you drink milk thistle tea everyday?
A: There is no standardized dosage or recommended intake for milk thistle tea, but it’s generally considered safe if consumed in moderation. Milk thistle supplements, for reference, are tolerated at doses of up to 700 mg, 3 times per day for 24 weeks ( 1 ).

Q: What are the medicinal uses of thistle?
A: Historically, people have used milk thistle for liver disorders and gallbladder problems. Milk thistle is promoted as a dietary supplement for hepatitis, cirrhosis, jaundice, diabetes, indigestion, and other conditions.

Q: Is Scotch thistle invasive?
A: Bull, musk, plumeless, and Scotch thistles are annual and biennial nonnative plants in the sunflower family that are considered invasive.

Q: Why is Scotch thistle a problem?
A: It drastically reduces productive rangeland by out competing desirable forage species. It can be so thick that it becomes an impenetrable, thorny barrier for ranchers, cattle, wildlife and recreationists. Although, scotch thistle is considered a biennial weed, it can behave as an annual or a short-lived perennial.

Q: Is the thistle plant good for anything?
A: Thistle is a very beneficial plant for pollinators. Bees, flies, beetles, and butterflies all like the nectar of the thistle flowers.

Q: How do you control Scotch thistle?
A: Isolated plants should be removed using a hoe or mattock (chipping or grubbing). Remove as much of the taproot as possible so that regrowth does not occur. Cultivation is effective on seedlings or young rosettes if they are uprooted.

Q: Does thistle harm the environment?
A: Thistles are notorious for draining nutrients from the soil around them, so they can be very damaging to pastures and crops. They also use large amounts of water, so they can make soil dry and increase erosion potential. Global climate change has created a unique opportunity for thistles.

Q: How does Scotch thistle spread?
A: As with all thistles, seed heads are a collection of florets, and each seed is attached to a pappus which allows it to be blown in the wind. When growing under good conditions, the flowering plant can get well over 1 m in height and takes up a lot of space in pasture due to its branching growth habit.

Q: Is Bull thistle the same as Scotch thistle?
A: Scotch thistle can be confused with bull thistle (Cirsium vulgaris), which is also sometimes called “Scotch thistle”” and is much more common in western Washington. Scotch thistle is more densely covered with white hairs tends to be taller and the stems have “”wings”” along the entire length unlike bull thistle.”

Q: Is it illegal to grow thistles?
A: It is unlawful to allow the following harmful weeds, listed in the Weeds Act 1959, to spread onto agricultural land: Common ragwort, spear thistle, broad-leaved dock, curled dock, and creeping field thistle. Under section 14 of the Wildlife and Countryside Act 1981, it is an offence to plant or grow Japanese Knotweed.

Q: Do cows eat Scotch thistle?
A: Thistles are generally avoided by stock. However goats eat thistles at both the rosette and flowering stage as well as post-flowering. Horses, and sometimes cattle graze the flower which can reduce the amount of seed.

Q: Why is bull thistle a problem?
A: Why is bull thistle a problem? Bull thistle outcompetes native plants and desir- able wildlife. It invades most disturbed habitats such as pastures, roadsides and ditch banks, and grows in dense thickets. Bull thistle is an economic threat by reducing hay quality.

Q: Is bull thistle poisonous to humans?
A: Bull thistle is moderately toxic. Its seedlings are edible after cooking, but it contains oxalic acid, which can be toxic if eaten for a long time. Its flowers are gorgeous and its fruits are striking.

Q: What does Scottish thistle taste like?
A: Taste. I describe the taste of the root as bland slightly sweet, the stem as fresh and bitter (far nicer than burdock stem which I find way too astringent), leaves are more bland than the stem, this is because usually plants with spikes don’t also need a strong taste to deter predators.

Q: Is Scottish thistle poisonous?
A: Rub the “wool” off and enjoy, raw or cooked. All thistles in the genus Cirsium, and the genus Carduus, are edible. Or said another way, there is no poisonous true thistle, but not all of them are palatable. In the second year plant the inner core of the flower stalks is quite tasty and not that much work.

Q: Are thistle weeds good for anything?
A: Thistle is a very beneficial plant for pollinators. Bees, flies, beetles, and butterflies all like the nectar of the thistle flowers. We have these all over our yard here in Maine.

Q: Can humans eat thistle?
A: In addition to the root, the stems are edible, when peeled. However, the thistle contains inulin, which gives some people digestive issues.

Q: Are thistles poisonous to touch?
A: This method may be more difficult due to the fact they have hairs that cause a painful irritating sting and spread by underground stems. Thistles are a noxious weed and while not particularly poisonous they are harmful if touched or swallowed.

About the author

Samuel is a gardening professional and enthusiast who has spent over 20 years advising homeowners and farm owners on weed identification, prevention and removal. He has an undergraduate degree in plant and soil science from Michigan State University.