Are Thistle Flowers Poisonous?

Last Updated on December 26, 2022 by Derek

True thistle is not poisonous when ingested or upon skin contact. However, not all thistle varieties are palatable. The thorns and green coating on thistle leaves harbor inulin, which is a complex natural compound that if ingested may cause digestive issues. In animals like cows, sheep, or dogs, thistle consumption can cause mild stomach upset and loose stools. However, if consumed in excess, it can lead to death.

Research shows that all the parts of a thistle plant are edible. This provided you can get past the distinct thorns found on the flowers. Thistle flowers, particularly the Bull thistle are common and like growing along with other plants. 

Purple Thistle Flowers

The purple thistle plant part of a large family of the same species. Any thistle plant you see belongs to the Onopordum, Cirsium, Carthamus, or Carduus genus. These wild-looking plants are native to Europe and Asia. 

Some thistles are labeled weeds because of their fast rate of reproduction and toxic qualities. Note, however, not all thistle flowers grow rapidly or are toxic. In fact, that thistle-like plant in your flower garden or landscaping could make one delicious treat.

Video – Field thistle flowers are edible and medicinal

What can Thistle be used for? Purple thistle uses.

Table – Thistle Flowers facts and figures

Below is a brief informational table illustration 

Common Thistle NamesScientific NameUnique FeaturesGrowing Conditions
Bull ThistleCirsium vulgareThe pink-purple flower has a leathery coating. 
Has green, deeply lobed, prickly leaves.
Needs good soil and at least 6 hours under the sun to thrive beyond maturity.
Canada ThistleCir. arvenseHas several small-sized well-arranged green leaves. 
The leaves have stiff yellow-colored spikes around the edges.
Produces flat-shaped brownish, long-haired fruits.
Develops well under total sun exposure. No need for regular irrigation and can grow in any type of soil.
Distaff ThistleCarthamus lanatusHas straw-colored stems that can be between 2ft. to 4 ft. long. 
Its flower heads are cupped by five or more spikey leaves.
The stem and leaves feature cobweb-like hairs.
Grows well under complete sun exposure and requires little to no after-care and maintenance.
Musk ThistleCarduus nutansHas hairless leaves that have spikes and are adorned with silver-colored edges.
Has a purple flower that also has spikes.
Can Grow up to 7 feet tall.
Thrives in dry or moist soil and under complete sun exposure.
Scotch ThistleOnopordum AcanthiumHas large green-gray leaves with a thick hairy coating.
Produces round purple-colored flowers.
Its stems can grow up to 9ft. tall and have spiny wings.
Thrives well in sandy, drained, or stony soil and needs total sun exposure to thrive.
Italian thistleCarduus pycnocephalusCan grow up to 8ft. tall.
Blooms in clusters with about five lower heads each.
Has cylinder-shaped, pink-colored flowers.
Grows well under full sun and no need for weed control.
Purple Star ThistleCentaurea calcitrapaHas stems and leaves that are covered with cobweb-like hairs.
Has rosette-shaped leaves with circular spines at the center.
Produces Lavender to deep purple flowers.
Can grow well in any type of soil but requires weed control due to high reproduction rate.

What Do Thistle Flowers Smell Like?        

Thistle flowers all produce a distinct smell. The Globe thistle variety, for example, has a terrible smell that is likened to a dog or cat poop. The musk thistle variety, on the other hand, has a sweet and musky fragrance.

Pink Thistle Flowers

Invasive species in the Echinops, Cirsium, Carduus, and Sonchus genera develop dense pink or pink-purple flowers.

Pink thistle flowers are preferred for their attractive shade. Florists use pink thistle flowers for weddings, birthdays, valentine’s day, funerals, and other special occasions.

Scottish Thistle Flower

A common legend states that during the war, centuries ago, the Scottish thistle saved sleeping Scott warriors from an ambush by the Nordish army. This explains where and why the Scottish thistle is named so.

The Scottish thistle has for over 500 years been the country’s national flower and symbol and there are even Scottish Thistle poems. Also known as Onopordum acanthium, the Scottish thistle originally hails from the European and western parts of Asia.

Where Do Thistle Plants Grow?

Thistle plants naturally grow all over the world where the climate is relatively warm and dry. Most thistle plants grow in huge numbers. For this plant to thrive, it requires mildly moist or dry soils.

It grows well along with other plants in open spaces where there’s pasture, logged areas, trails, cultivated land, and tall grass. Savannas, old fields, the roadside, and forest edges make for ideal spots where thistle plants can grow undisturbed. 

All thistle varieties prefer exposed sunny areas. They hold up well in a wide range of weather and soil conditions. Whether planted in rocky, moist, or dry soil, any thistle plant will grow well past the maturity stage. 

Thistle plants for the garden should be well controlled as they considered invasive. Growing thistles in pots is a good alternative, or larger square containers. It’s good to have some wild in your garden!

Infographic – How to identify thistles

You can embed this infographic on your site provided the link back to Essential Garden Guide is left intact:

Types of thistle weeds
How to identify thistles (UK)

How to Identify Thistles

Thistle varieties come in different shapes and sizes but, they also share different similarities. To distinguish, one thistle variety from other plants, look at the shape of the leaves, the color of the flowers, their spikes, and the general color of the plant.

Common thistle plants like the Musk thistle, bull thistle, distaff thistle, Canada thistle, and scotch thistle grow to a height of between 2ft tall and 9ft tall.  Most types have the characteristic purple thistle flower. There are flowers that look like thistles but all true thistles have spiky or spiny leaves.

Is a Thistle a Wildflower?

Thistle plants are considered wildflowers because of how invasive they are and how difficult it is to get rid of them. However, there exists thistle varieties that grow only in manageable conditions, have no toxic qualities, and are easy to do away with should you want to bring in different plants in your garden. 

When is Blue Thistle Flower Season?

Blue thistle flowers bloom from July, all through to August every year. They are perennial plants that make excellent companions for other plants. They thrive well in difficult conditions and require minimal care. Blue thistle varieties include Snapdragons, Wormwoods, globe thistle, and phlox.

Is Blue Thistle a Flower?

Blue thistle is classified not as a flower but as dicotyledonous. Scientifically known as Eryngium planum, this variety is also labeled a perennial herbaceous weed originally from Eastern Europe. The blue thistle is a member of the parsley family and not a flowering weed as most people perceive.

Thistle Flowers Meaning

Blue thistle meaning in the Bible is a symbol of hardships and the wilderness. Different references therein refer to thistle as the thorny or prickly plant. 

Universally, thistle attributes to pain, pride, aggressiveness, and protection. It can also mean weakness and poverty. The thistle spiritual meaning in some cultures can depict brilliance and might.

Other resources relating to Thistles:

Thistle | plant – Encyclopedia Britannica

The Trouble with Thistles | Nature’s Poisons

Milk Thistle and Hemlock: The Prickly and the Poisonous

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