Thistle
Thistle is the common name of a group of flowering plants characterized by leaves with sharp spikes on the margins, mostly in the family Asteraceae. Prickles can also occur all over the planton the stem and on the flat parts of the leaves. These prickles protect the plant from herbivores. Typically, an involucre with a clasping shape similar to a cup or urn subtends each of a thistle's flower heads. The typically feathery pappus of a ripe thistle flower is known as thistle-down.
The spininess varies considerably by species. For example, Cirsium heterophyllum has very soft spines while Cirsium spinosissimum is the opposite. Typically, species adapted to dry environments are more spiny.
The term thistle is sometimes taken to mean precisely those plants in the tribe Cardueae, especially the genera Carduus, Cirsium, and Onopordum. 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.
A thistle is the floral emblem of Scotland and Lorraine, as well as the emblem of the Encyclopædia Britannica.
Taxonomy
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
- Carthamus – distaff thistle
- Centaurea – star thistle
- Cicerbita – sow thistle
- Cirsium – melancholy thistle, creeping thistle, spear thistle, and others
- Cnicus – blessed thistle
- Cynara – artichoke, cardoon
- Echinops – globe thistle
- Galactites – milk thistle
- Notobasis – Syrian thistle
- Onopordum – cotton thistle, also known as Scots thistle
- Scolymus – golden thistle or oyster thistle
- Silybum – milk or St. Mary's thistle
- Sonchus – sow thistle
- Salsola – Russian thistle, Tartar thistle, or tumbleweed, plants formerly classified in the genus Kali
- Argemone mexicana – flowering thistle, purple prickly poppy
- Eryngium – certain species include the word thistle, such as beethistle, E. articulatum
- Dipsacus fullonum – German names include Hausdistel, Kardendisteln, Roddistel, Sprotdistel and Weber''distel''
Ecology
Thistles and thistle-seed feeders provide important sustenance for goldfinches and the flowers are strongly favoured by many butterflies besides fritillaries such as the monarch, skippers, and the various types of tiger swallowtail. Hummingbirds will feed on the flowers of the biennial species, which feature large flowers, as compared with the perennial creeping thistle.
Some thistles, for example Cirsium vulgare, native to Eurasia, have been widely introduced outside their native range. Control measures include Trichosirocalus weevils. 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. Another approach towards controlling thistle growth is using thistle tortoise beetles as a biological control agent; through feeding on thistle plants, thistle tortoise beetles skeletonize the leaves and damage the plant.
Thistles are important nectar sources for pollinators. Some ecological organizations, such as the Xerces 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. Although such organizations focus on the benefits of native thistles, certain non-native thistles, such as Cirsium vulgare in North America, may provide similar benefits to wildlife.
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 a UK plants survey conducted by the AgriLand project supported by the UK Insect Pollinators Initiative. Bull thistle was a top producer of nectar sugar in another study in Britain, ranked third with a production per floral unit of.
Uses
and medieval writers thought it could return hair to bald heads and that in the early modern period it was believed to be a remedy for headaches, plague, cancer sores, vertigo, and jaundice.Cuisine
In the Beira region of Portugal, thistle flowers are used as rennet in cheese 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.Economic significance
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 of Cirsium, Carduus, Silybum and Onopordum. 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.The genus Cynara includes the commercially important species of artichoke. Some species regarded as major weeds are sources of vegetable rennet used in commercial cheese making. Similarly, some species of Silybum that occur as weeds are cultivated for seeds that yield vegetable oil and pharmaceutical compounds such as Silibinin.
Other thistles that nominally are weeds are important honey plants, both as bee fodder in general, and as sources of luxury monofloral honey products.
Culture
Symbolism
Scottish thistle
The thistle has been the national emblem of Scotland since the reign of King Alexander III.According to legend, an invading Norse 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 the Battle of Largs, which marked the beginning of the departure of King Haakon IV of Norway who, having control of the Northern Isles and Hebrides, had harried the coast of the Kingdom of Scotland for some years.
The thistle was used on silver coins first issued by King James III in 1474 as a Scottish symbol and national emblem. In 1536, the bawbee, a sixpence in the pound Scots, was issued for the first time under King James V; it showed a crowned thistle. Thistles continued to appear regularly on Scottish and later British coinage until 2008, when a 5p 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 oldest chivalric order of Scotland, has thistles on its insignia and a chapel in St Giles's Kirk, Edinburgh, dubbed the Thistle Chapel. The thistle is the main charge of the regimental badge of the Scots Guards, the oldest regiment in the British Army.
Both the Order of the Thistle and the Scots Guards use the motto Nemo me impune lacessit, the motto of the House 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, the grant of arms to the new National Bank of Scotland stipulates that the shield be surrounded by thistles and "thistle" is used as the name of several Scottish football clubs. Since 1960, a stylised thistle, also representing the Scottish Saltire, has been the logo of the Scottish National Party. The thistle is also seen as the logo for Scottish Rugby. Many businesses in Scotland choose this symbol to represent their organization.
Since 2013, a different stylised thistle, crowned with the Scottish crown, has been the emblem of Police Scotland, and had long featured in the arms of seven of the eight pre-2013 Scottish police services and constabularies, the sole exception being the Northern Constabulary. As part of the arms of the University of Edinburgh, the thistle appears together with a saltire on one of the escutcheons of the Mercat Cross in Edinburgh. The coat of arms and crest of Nova Scotia, 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 a badge consisting of a Tudor rose "dimidiated" with a Scottish thistle and surmounted by a royal crown.
As the floral emblem of Scotland it appears in the Royal Arms of the United Kingdom thereafter, and was included in the heraldry of various British institutions, such as the Badge of the Supreme Court of the United Kingdom alongside the Tudor rose, Northern Irish flax, and Welsh leek. This floral combination appears on the present issues of the one pound coin. Beside the Tudor rose and Irish shamrock the thistle appears on the badge of the Yeomen of the Guard and the arms of the Canada Company. Issues of the historical florin showed the same flora, later including a leek.
The thistle is also used to symbolise connection with Scotland overseas. For example, in Canada, it is one of the four floral emblems on the flag 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, and Annapolis, Maryland features the thistle in its flag and seal. The thistle is also the emblem of the Encyclopædia Britannica and Jardine Matheson Holdings Limited.
Which species of thistle is referred to in the original legend is disputed. Popular modern usage favours cotton thistle, 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, an abundant native species in Scotland, is a more likely candidate. Other species, including dwarf thistle, musk thistle, and melancholy thistle have also been suggested.