Spanish Thistle

Biological Name:

Carduus pycnocephalus (Spanish-Thistle)

Natural Habitat:

Spanish-Thistle: This plant is native to North America and can be found in a variety of habitats, including fields, roadsides, and waste areas.


Spanish-Thistle also known as Carduus is a plant that is native to grassland and prairie regions of North America. It is an annual herb that can grow up to three feet tall and it has small oval-shaped leaves and showy pink or purple flowers that bloom in the summer. The plant is known for its spiny thistle-like leaves and it is often found in disturbed or degraded habitats.

Frequently Asked Questions (FAQs)

Q: Do thistles grow in Spain?
A: The Golden Thistle, locally known as cardillo, is one of the most appreciated wild vegetables in Central Spain [2] and other Spanish regions [22].

Q: Is it illegal to have thistles in your garden?
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: Should I leave thistles in my garden?
A: Creeping thistle can become a serious weed as it spreads using lateral roots which are brittle and readily re-shoot if broken. As these large plants compete for light, water and food you may want to control this plant in lawns and borders.

Q: Are thistles good for wildlife?
A: Thistles provide a succession of micro-environments and food for a range of birds such as siskin and insects feeding on green leaves, flower heads, dead heads and stems.

Q: Are thistle plants invasive?
A: Bull, musk, plumeless, and Scotch thistles are annual and biennial nonnative plants in the sunflower family that are considered invasive. Plumeless and Scotch thistles are listed as noxious weeds in both Arizona and New Mexico.

Q: Are thistles good for soil?
A: Thistle (Cirsium arvense) The thistle family is high in potassium and can therefore benefit the soil when tilled back in or added to the compost pile.

Q: What time of year do thistles flower?
A: Habit The perennial sow thistle flowers from late July until early October, with some seeds ready to germinate just 4 days after flowering. They can even mature on stems that are cut down and left to dry. Each plant has on average 13,000 seeds. The plant dies down in winter, and sprouts from the thick root in spring.

Q: What is thistle plants good for?
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. We try to tolerate them when they pop up in out-of-the-way spots, but they’ve even taken to growing all around the backdoor….

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: Is thistle poisonous to humans?
A: It may look dangerous, but it is not poisonous. In fact, it has an edible stem.

Q: Do thistle plants spread?
A: Not only do thistles spread via seed, their thick, white roots also spread underground, causing new plants to pop up on a regular basis. Weeds that spread in this fashion should never be tilled or the problem will become worse as each root piece the tilling process leaves behind will develop into a new plant.

Q: Does thistle attract bees?
A: We found that the non-native thistle was the most attractive of the plant species to visiting bee species. However, there was no effect of experimental treatment (presence of thistle) on bee abundance or visitation rate (bees per unit floral area per sample) to native plant species.

Q: What does thistle tell you about your soil?
A: 10. Sow thistle (Sonchus oleraceus) is often indicative of dry, heavy, acidic, and iron deficient soil.

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

Q: Is thistle toxic to dogs?
A: If given too often and at too high a dose, milk thistle can also actually cause liver damage and suppress function. This is one of the primary reasons this supplement should not be given to health dogs, but rather only to dogs who have existing liver problems.

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.

Q: Can you touch thistles?
A: Telling Milk Thistle and Hemlock Apart It’s best not to touch it at all, as it contains the poison that Socrates was forced to drink as capital punishment. It can easily kill you, too, if ingested. Beautiful as it is, don’t let it remain in your yard if you have children around who might accidentally pick or eat it.

Q: Are thistles good for the garden?
A: And sometimes it is used more broadly to refer to a wider range of prickly flowering plants. However you define the term, thistles can be very useful and attractive plants for your garden. What is this? Even those commonly considered to be weeds can be great choices to consider.

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: How many varieties of thistle are there?
A: Thistles have all disc flowers that are shaped into long tubes. About 200 species are known worldwide from North America, Europe and Asia.

Q: How fast does thistle spread?
A: Once the plant becomes established, roots are the most important means of propagation. Canada thistle has an extensive underground root system that may penetrate the soil to a depth of 10 feet or more and grow laterally 12 to 15 feet per year.

Q: Are thistles self seeding?
A: Thistles are pretty much self-fertile so will readily produce seeds and reproduce this way too. Seeds has a rapid germination and higher temperatures during the Summer months increase the germination rate. Thistles can take over a variety of areas including uncultivated soil and grassland including pastures.

Q: Do you cut back thistles?
A: As with most perennials, cut back the globe thistles completely close to the ground in autumn. The roots overwinter in the soil and sprout fresh the next spring.

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.