Cirsium vulgare (Savi) Ten., Spear Thistle

Account Summary

Growth form and preferred habitats

A species capable of vigorous growth, this stout, conspicuous, winter-green, biennial or monocarpic perennial thistle produces branching flowering stems 30-200 cm high that are continuously winged and are fiercely armed with very sharp prickles. The stems are also ribbed with two spiny ridges and are covered with a coat of woolly hairs, as are the under-surfaces of the very spiny leaves that are also very prickly and hairy on the upper surface and possess a long, narrow terminal lobe armed with a very sharp spine (Hutchinson 1972; Garrard & Streeter 1983). The basal leaves, 15-30 cm long, are lanceolate, pinnately lobed, each lobe ending in a long spine and with smaller prickles on their margins. They are also bristly above and white, woolly-haired beneath (Melderis & Bangerter 1955). The flower-heads (capitula) are large, purplish, almost sessile, and are held in small clusters. Each capitulum is surrounded by an egg-shaped involucre of 10-15 rows of spiny, green bracts, all of which end in a long, hard, sharp prickle.

C. vulgare most commonly occurs in coarse, weedy vegetation on disturbed habitats, roadside verges, waste ground and on exposed soils including cultivated land, but it is also frequent around dung patches in pastures, where it sometimes forms large, dense stands. It is less commonly found in hedges and on the banks of streams and rivers. C. vulgare prefers well-drained, constantly moist or damp, but not dry ground. It is a very typical plant of fertile, base-rich or calcareous, fairly nitrogen-rich soils (Garrard & Streeter 1983). It is said to be indifferent to P and K levels, but it avoids extremes of soil fertility and, while mainly found in well-lit situations, it can tolerate partial shade (Klinkhamer & de Jong 1993).

Spear Thistle often occurs along with C. arvense (Creeping Thistle), but is less common than the latter in permanent pastures, most likely because it lacks the perennial creeping root system of C. arvense. Both species form short-lived populations and they sometimes occur in temporary habitats (van Leeuwen (1981). These two species are among those scheduled by agriculturalists as injurious or noxious weeds requiring control. Both have spiny stems and leaves which make them unpalatable to stock other than horses and donkeys, and their excellent fecundity and dispersal abilities allow them to invade bare patches in overgrazed pastures (Garrard & Streeter 1983; Grime et al. 1988, 2007; Klinkhamer & de Jong 1993).

In addition, pasture grazing by sheep reduces competition on C. vulgare, allowing it to display increased growth, flowering and seed production and it also promotes seedling survival (Forcella & Wood 1986). Rabbits help to limit Spear Thistle by eating its spiny leaves, especially in winter and early spring, and by also attacking the erect stem they can significantly reduce seed output, even though secondary flowering stems may sometimes be formed (Klinkhamer & de Jong 1993).

Fermanagh occurrence

C. vulgare has been recorded in 388 Fermanagh tetrads, 73.5% of those in the VC. Indeed, so successful is the dispersal of Spear Thistle, it is absent in Fermanagh only from well-managed meadows and pastures, waterlogged soils, very exposed upland and deeply shaded woods.

Flowering reproduction

Reproduction is entirely by seed, flowering taking place from July onwards and continuing into October. The flowers are perfect (ie bisexual or hermaphrodite) and are mainly pollinated by honey bees and bumble bees, although Lepidoptera spp. and other insects also visit to obtain nectar concealed at the base of the long corolla tube on each flower. However, in the absence of insect visitors, or when isolated individuals occur, C. vulgare can self-pollinate or produce seed apomictically. The achenes (single-seeded dry fruits) are glabrous and each has an attached pappus of very many, feathery branched hairs that acts as a parachute enabling wind dispersal. When the fruits are first formed and remain in the flower-head, the tightly packed collection of feathery pappi makes the head look just like a shaving brush (Melderis & Bangerter 1955)!

A Dutch experimental study found that achenes produced by cross-pollinated flowers were lighter in weight than those from which insects were excluded. Cross-pollinated achenes also germinated slower and survival until the one-year-old plant stage from these achenes was lower (van Leeuwen 1981). Achenes from self-pollinated flowers showed differing germination behaviour compared to cross-pollinated achenes, resulting in better establishment of plants on the site of the mother plant. The study did not indicate whether this was due to phenotypic or genotypic properties of the two achene types (van Leeuwen 1981), however, self-pollinated, or to a greater extent, apomictic seeds are known to be genetically more adapted to local environment conditions. "Cross-pollination in C. vulgare results in a greater number of achenes which are better dispersed and possibly genotypically more differentiated, ie, equipped for the colonisation of sites differing from the site of the motherplant and situated at some distance from that site. At the start of the population with one individual, a lower number of heavier, less-well dispersed achenes with a locally adapted genotype ensure the quick build-up of the population. Later, when the site might become less suitable, cross-pollinated achenes are produced." (van Leeuwen 1981).

Seed production per plant varies very considerably, from up to 3,200 seeds per plant in ungrazed ground, in comparison with up to 8,400 per plant in grazed pastures (Forcella & Wood 1986). Largely thanks to the vast numbers of seeds produced, the inefficiencies of wind-dispersal are overcome. Although the plumed pappus is firmly attached to the achene, experimental measurements have found that around 65% of seeds land within 2 m of the parent plant and only about 10% disperse more than 32 m. It is probably only a tiny proportion of these which reach higher levels above the ground and may then travel very long distances (Klinkhamer & de Jong 1993).

Seed germination

Seeds can germinate throughout the year, usually with a small peak after autumn rains and a much larger one in April and May. As with other weed species, patches of bare soil are essential for seedling survival and establishment and rosette survival declines when vegetation cover exceeds 70%, or when tall herbs and grasses compete and prevail.

Seed longevity

In their detailed Biological Flora account in The Journal of Ecology, Klinkhamer & de Jong (1993) did not believe the evidence supported the existence of a soil seed bank. Experimental studies in Canada, however, showed that some seed stored in shaded conditions in a clay-loam soil remained viable for 30 months, which the authors concluded was evidence of a soil seed bank for the species (Doucet & Cavers 1996).

Fossil history

As described by Godwin (1975), C. vulgare demonstrates a very standard type of fossil record for a weed species, which is based on its fruits that stretch back to the Cromer Forest Beds series, and appear again in the Hoxnian and the Ipswichian interglacials. There is an isolated record from the Late Weichselian ice age from East Anglia and all records from the current Flandrian interglacial are from later periods and have been found associated with archaeological digs dating from the Late Bronze Age, the Roman period and one mediaeval site (Godwin 1975). The pattern does not indicate periglacial survival, but rather reflects the considerable dispersal ability of the species and its association with disturbed, open habitats. Although it is very closely tied to archaeological sites, it is assumed to be native. If this is not proven by the existing fossil record, then it certainly would qualify as an archaeophyte.

Weed control

Timing of intervention is important in terms of control. Mowing of meadows just before seed dispersal is an effective way of reducing population size as the plant does not recover well. Similarly, herbicide control of C. vulgare in Australia with dicamba was most effective just after the start of autumn rains, a period coinciding with naturally high seedling mortality due to competition from neighbouring plants (Forcella & Wood 1986). Because seed can germinate throughout the year, herbicide control generally requires several well-spaced applications across the seasons. When an infestation is recent and not sufficiently severe nor widespread to necessitate the use of herbicide, spudding out of the young rosettes by hand is considered the best method of control.

C. vulgare is not a serious problem in arable crops requiring a spring seedbed since tillage eradicates rosettes that established in the preceding summer or autumn. However, it is a problem in autumn planted crops such as cereals and clover. Biological control in N America used Trichosirocalis horridus, the Rosette weevil, which feeds on the crown of the thistle. This weevil, a native European species, was studied extensively by the US Department of Agriculture before introduction, to ensure that it would not damage other desirable plants in the US.

British and Irish occurrence

Whatever one thinks of the seed dispersal mechanism, it works sufficiently well that C. vulgare is extremely widespread, locally abundant and persistent, and occurs in every VC and in almost every hectad in both Britain and Ireland.

European and world occurrence

C. vulgare is common and widely distributed in all of Europe, W Asia and N & S Africa, including Ethiopia and S Arabia. It almost reaches 68^oN in Scandinavia, is absent from Iceland and stretches east to Turkestan. It is introduced in N America, Chile, Argentine, Australia and New Zealand (Hultén & Fries 1986, Map 1867).

Uses

Thistles of all sorts when beaten or crushed to break the spines are nutritious fodder for cattle and horses (Grieve 1931). The young shoot, root and flower stalk of Spear Thistle, peeled of its prickles and then boiled in salted water or fried in butter, can be served as a vegetable (Launert 1981).

Names

The name 'Cirsium' is said to be derived from the Greek 'kirsos', a swollen vein, alluding to the reaction when the skin is pricked by the spines (Hyam & Pankhurst 1995). There may be a connection to Dioscorides and the old manuscript herbals since the Greek name was given by him to a plant (now thought to be Carduus pycnocephalus (Plymouth Thistle)), used for the enlargement of veins (Gilbert-Carter 1964). The Latin specific epithet 'vulgare' just means 'common', which the species undoubtedly is. In older references, this thistle is named Carduus lanceolatus (see below) or Cirsium lanceolatus

The English common name 'Spear Thistle' is a translation by Gerard (1597), to whom the first record is credited, of 'Carduus lanceolatus', the name which Jacob Dietrich (also known as Jacobus Theodorus and Tabernaemontanus), gave to this plant in his Neuw Kreuterbuch, dated 1588-1591 (Grigson 1955, 1987; Henrey 1975). Undoubtedly the long, rather narrow terminal portion of the leaf, ending in a sharp, stout, yellow spine is responsible for the common name of the plant, 'Spear Thistle'. The name 'Thistle' is derived from the Anglo-Saxon 'pistel', itself from 'pydan', meaning 'stab' or 'to stab' (Prior 1879). 'Thistle' in Old English is 'thistel', with similar names in other Germanic languages. Grigson (1974) says it is, "a diminutive of a Germanic 'thihsta', from an Indoeuropean base meaning to prick".

Grigson (1955, 1987) lists as many as twelve alternative English common names from around B & I, none of which he provides any explanation for their derivation or attachment to the plant. Several of the names listed by him refer to animals, including 'Bird Thistle', 'Boar Thistle', 'Bull Thistle', 'Horse Thistle' and 'Cuckoo Buttons'.

There are 17 alternative English common names provided by Vickery (2019) and he mentions that 'Bird Thistle' is, "because goldfinches and other birds feed on the seeds". He qualifies this suggestion by saying 'Bird Thistle' may simply be a form or corruption of 'Bur Thistle' or 'Blue Thistle', two other local names. The word element 'dasle', 'dashel' , 'dashle' or 'distle' occurs in the list of names, eg 'Horse-dashel', and clearly must be a substitute for 'thistle', as is 'fistle' in 'Boar-fistle', a local name from Cheshire (Vickery 2019).

Threats

None.

References

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