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This article is about the plant, for other uses see Thistle (disambiguation).

Milk thistle flowerhead

Thistle is the common name of a polyphyletic group of flowering plants characterised by leaves with sharp spines or prickles on the margins, mostly in the plant family Asteraceae. Their prickles often occur all over the plant, including on the stem and flat parts of the leaf. These are an adaptation to protect the plant against herbivorous animals, discouraging them from feeding on the plant.

In the language of flowers, the thistle (like the burr) is an ancient Celtic symbol of nobility of character as well as of birth, for the wounding or provocation of a thistle yields punishment. For this reason the thistle is the symbol of the Order of the Thistle, a high chivalric order of Scotland.

Another story is that a Viking attacker stepped on one at night and cried out, so alerting the defenders of a Scottish castle.^[1] Whatever the justification, the national flower of Scotland is the thistle - specifically Onopordum acanthium, the Scots thistle. It is found in many Scottish symbols and in the names of several Scottish football clubs.

Carduus is the Latin for a thistle (hence cardoon), and Cardonnacum is the Latin for a place with thistles. This is believed to be the origin of name of the Burgundy village of Chardonnay, Saône-et-Loire, which in turn is thought to be the home of the famous Chardonnay grape variety.

Thistledown, a method of seed dispersal by wind. The tiny seeds are a favorite of goldfinches and some other small birds.

Genera in the Asteraceae with the word thistle often used in their common names include:

• Arctium – Burdock
• Carduus – Musk Thistle and others
• Carlina – Carline thistle
• Centaurea – Star thistle
• Cicerbita – Sow thistle
• Cirsium – Common Thistle, Field Thistle and others
• Cnicus – Blessed thistle
• Cynara – Artichokes, Cardoon
• Echinops – Globethistle
• Notobasis – Syrian thistle
• Onopordum – Cotton thistle, also known as Scots thistle or Scotch thistle
• Scolymus – Golden thistle or oyster thistle
• Silybum – Milk thistle
• Sonchus – Sow thistle

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Thistles

Plants in families other than Asteraceae which are sometimes called thistle include:

• Salsola – Saltwort, tumbleweed or Russian thistle (family Amaranthaceae)

South Island, New Zealand