Thistle is the common name of a group offlowering plants characterized byleaves with sharp spikes on the margins, mostly in the familyAsteraceae. Prickles can also occur all over the plant – on the stem and on the flat parts of the leaves. These prickles protect the plant fromherbivores. Typically, aninvolucre with a clasping shape similar to a cup or urn subtends each of a thistle'sflower heads. The typically featherypappus of a ripe thistle flower is known asthistle-down.[1]
The spininess varies considerably by species. For example,Cirsium heterophyllum has very soft spines whileCirsium spinosissimum is the opposite.[2] Typically, species adapted to dry environments are more spiny.
The term thistle is sometimes taken to mean precisely those plants in the tribeCardueae (synonym: Cynareae),[3] especially the generaCarduus,Cirsium, andOnopordum.[4] However,plants outside this tribe are sometimes also called thistles.
Biennial thistles are particularly noteworthy for their high wildlife value, producing copious floral resources for pollinators, nourishing seeds for birds like the goldfinch, foliage for butterfly larvae, and down for the lining of birds' nests.[5][6][7]
A thistle is thefloral emblem ofScotland andLorraine, as well as the emblem of theEncyclopædia Britannica.
Genera in theAsteraceae with the word thistle often used in their common names include:[citation needed]
Plants in families other than Asteraceae which are sometimes called thistle include:
Thistle flowers are the favorite nectar sources of thepearl-bordered fritillary,small pearl-bordered fritillary,high brown fritillary, anddark green fritillary butterflies.[8]Thistles and thistle-seed feeders provide important sustenance forgoldfinches and the flowers are strongly favoured by many butterflies besides fritillaries such as themonarch,skippers, and the various types oftiger swallowtail. Hummingbirds will feed on the flowers of the biennial species, which feature large flowers, as compared with the perennialcreeping thistle.[citation needed]
Some thistles, for exampleCirsium vulgare, native to Eurasia, have been widely introduced outside their native range.[9] Control measures includeTrichosirocalusweevils. A problem with this approach, at least in North America, is that the introduced weevils may affect native thistles at least as much as the desired targets.[10] Another approach towards controlling thistle growth is usingthistle tortoise beetles as a biological control agent; through feeding on thistle plants, thistle tortoise beetles skeletonize the leaves and damage the plant.[11]
Thistles are important nectar sources for pollinators. Some ecological organizations, such as theXerces Society, have attempted to raise awareness of their benefits to counteract the general agricultural and home garden labeling of thistles as weeds. The monarch butterfly,Danaus plexippus for instance, was highlighted as traditionally relying upon taller large-flowered thistle species such as Tall thistle,Cirsium altissimum, for its migration.[6] Although such organizations focus on the benefits of native thistles, certain non-native thistles, such asCirsium vulgare in North America, may provide similar benefits to wildlife.[7]
Some prairie and wildflower seed production companies supply bulk seed for native North American thistle species for wildlife habitat restoration, although availability tends to be low. Thistles are particularly valued by bumblebees for their high nectar production.Cirsium vulgare was ranked in the top ten for nectar production in aUK plants survey conducted by the AgriLand project supported by the UK Insect Pollinators Initiative.[7] Bull thistle was a top producer of nectar sugar in another study in Britain, ranked third with a production per floral unit of (2323 ± 418μg).[5]
Pliny and medieval writers thought it could return hair to bald heads and that in theearly modern period it was believed to be a remedy for headaches,plague, cancer sores, vertigo, and jaundice.[12][13]
In theBeira region, thistle flowers are used as rennet incheese making. "Serra da Estrela" is not only the name of a mountain chain in this country, "Serra da Estrela" is also the name of one of the most appreciated cheeses made from sheep's milk.[14]
Thistles, even if one restricts the term to members of the Asteraceae, are too varied a group for generalisation. Many are troublesome weeds, including some invasive species ofCirsium,Carduus,Silybum andOnopordum.[15] Typical adverse effects are competition with crops and interference with grazing in pastures, where dense growths of spiny vegetation suppress forage plants and repel grazing animals. Some species, although not intensely poisonous, affect the health of animals that ingest them.[16][17]
The genusCynara includes the commercially important species ofartichoke. Some species regarded as major weeds are sources of vegetablerennet used in commercial cheese making.[18] Similarly, some species ofSilybum that occur as weeds are cultivated for seeds that yield vegetable oil and pharmaceutical compounds such asSilibinin.[19][20][21]
Other thistles that nominally are weeds are important honey plants, both as bee fodder in general, and as sources of luxurymonofloral honey products.[15][22][23]
The thistle has been the national emblem ofScotland since the reign ofKing Alexander III (1249–1286).[24][25]According tolegend, an invadingNorse army was attempting to sneak up at night upon a Scottish army's encampment. One barefoot Norseman stepped on a thistle and cried out in pain, thus alerting Scots to the presence of the invaders. Possibly, this happened in 1263 during theBattle of Largs, which marked the beginning of the departure of KingHaakon IV (Haakon the Elder) ofNorway who, having control of theNorthern Isles andHebrides, had harried the coast of theKingdom of Scotland for some years.[26]
The thistle was used onsilver coins first issued byKing James III in 1474 as aScottish symbol and national emblem.[27][28] In 1536, thebawbee, a sixpence in thepound Scots, was issued for the first time underKing James V; it showed a crowned thistle. Thistles continued to appear regularly on Scottish and later British coinage until 2008, when a5p coin design showing "The Badge of Scotland, a thistle royally crowned" ceased to be minted, though it remains in circulation.The Most Ancient and Most Noble Order of the Thistle, the highest and oldestchivalric order of Scotland, has thistles on its insignia and a chapel inSt Giles's Kirk, Edinburgh, dubbed theThistle Chapel. The thistle is the main charge of the regimental badge of theScots Guards, the oldest regiment in theBritish Army.
Both the Order of the Thistle and the Scots Guards use the mottoNemo me impune lacessit, the motto of theHouse of Stuart and referring to the thistle's prickly nature.Pound coins with this motto and a thistle were minted in 1984, 1989, and 2014. The combination of thistle and motto first appeared on the bawbee issued by King Charles II. In 1826, thegrant of arms to the newNational Bank of Scotland stipulates that the shield be surrounded by thistles and "thistle" is used asthe name of severalScottish football clubs. Since 1960, a stylised thistle, also representing the ScottishSaltire, has been the logo of theScottish National Party.[citation needed] The thistle is also seen as the logo for Scottish Rugby. Many businesses in Scotland choose this symbol to represent their organization.[29]
Since 2013, a different stylised thistle, crowned with the Scottish crown, has been the emblem ofPolice Scotland, and had long featured in thearms of seven of the eight pre-2013 Scottish police services and constabularies, the sole exception being theNorthern Constabulary. As part of the arms of theUniversity of Edinburgh, the thistle appears together with a saltire on one of the escutcheons of theMercat Cross in Edinburgh. The coat of arms and crest ofNova Scotia ("New Scotland"), briefly Scotland's colony, have since the 17th century featured thistles.Following his ascent to the English throne,King James VI of Scotland & I of England used abadge consisting of aTudor rose "dimidiated" with a Scottish thistle and surmounted by a royal crown.[30]
As the floral emblem of Scotland it appears in theRoyal Arms of the United Kingdom thereafter, and was included in the heraldry of variousBritish institutions, such as theBadge of the Supreme Court of the United Kingdom alongside the Tudor rose, Northern Irishflax, and Welshleek. This floral combination appears on the present issues of the one pound coin. Beside the Tudor rose and Irishshamrock the thistle appears on the badge of theYeomen of the Guard and the arms of theCanada Company. Issues of the historicalflorin showed the same flora, later including a leek.[citation needed]
The thistle is also used to symbolise connection with Scotland overseas. For example, in Canada, it is one of the four floral emblems on theflag of Montreal; in the US,Carnegie Mellon University features the thistle in its crest in honour of the Scottish heritage of its founder,Andrew Carnegie, andAnnapolis, Maryland features the thistle in its flag and seal. The thistle is also the emblem of theEncyclopædia Britannica (which originated in Edinburgh, Scotland) andJardine Matheson Holdings Limited (as the company was founded by two Scots).
Which species of thistle is referred to in the original legend is disputed. Popular modern usage favours cotton thistle (Onopordum acanthium), perhaps because of its more imposing appearance, though it is not native and unlikely to have occurred in Scotland in mediaeval times. The spear thistle (Cirsium vulgare), an abundant native species in Scotland, is a more likely candidate.[31][32] Other species, including dwarf thistle (Cirsium acaule), musk thistle (Carduus nutans), and melancholy thistle (Cirsium heterophyllum) have also been suggested.[33]
The thistle, and more preciselyOnopordum acanthium, is one of the symbols ofLorraine, together with its coat of arms which displays threeavalerions, and theCross of Lorraine.[citation needed]
Lorraine is a region located in northeastern France, along the border withLuxembourg andGermany. Before theFrench Revolution, a large part of the region formed theDuchy of Lorraine. In theMiddle Ages, the thistle was an emblem of theVirgin Mary because its white sap would bring to mind the milk falling from the breast of the Mother of God. It was later adopted as a personal symbol byRené of Anjou, together with the Cross of Lorraine, then known as the Cross of Anjou. It seems through his bookLivre du cuer d'amours espris that the Duke chose the thistle as his emblem not only because it was a Christian symbol, but also because he associated it with physical love.[34]
The thistle and the cross were used again by his grandson,René II, Duke of Lorraine, who introduced them in the region. The two symbols became hugely popular among the local people during theBattle of Nancy in 1477, during which the Lorrain army defeatedBurgundy. The Duke's motto was "Qui s'y frotte s'y pique", meaning "who touches it, pricks oneself", with a similar idea to the Scottish motto "Nemo me impune lacessit". Nowadays the thistle is still the official symbol of the city ofNancy, as well as the emblem of theAS Nancy football team, and theLorraine Regional Natural Park.[35][36]
Carduus is theLatin term for a thistle (hencecardoon,chardon in French), andCardonnacum is a Late Latin word for a place with thistles. This is believed to be the origin of name of theBurgundy village ofChardonnay, Saône-et-Loire, which in turn is thought to be the home of the famousChardonnay grape variety.
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