This site and its content are under development.

Achillea millefolium L., Yarrow

Account Summary

Native, common and locally abundant. Eurasian boreo-temperate, but widely naturalised in both hemispheres.

1881; Stewart, S.A.; Co Fermanagh.

Throughout the year.

Growth form and preferred habitats

A. millefolium is a very common, familiar and locally abundant, semi-rosette, wayside, strongly aromatic perennial with tough, far-creeping rhizomes that send up short, leafy, flowerless shoots to the surface at intervals (Hutchinson 1972). In winter, the small, bi- or tri-pinnate, fern- or moss-like, wintergreen leaf rosettes can often be found in short grass allowing the plant to be recorded all year round. Plants have a deep and extensive root system, some reaching down to depths of 20 cm, making the plant very drought resistant, but vulnerable to waterlogging (Grime et al. 1988, 2007).

A. millefolium thrives in rough grassland on fertile or moderately fertile soils where there is a degree of disturbance, as for example in grazed pasture, lawns, on roadsides, or more open waste ground, all situations where competition from large perennial species is limited. Although it grows and competes best on moderately fertile conditions, Yarrow can persist on poor, dry sandy soils as rather dwarfed, more hairy forms (Warwick & Black 1982). It is really absent only from strongly acidic, permanently waterlogged or very impoverished or heavily disturbed soils, or from deep shade (Garrard & Streeter 1983). It is tolerant of moderate grazing and trampling pressure and is probably avoided by horses and cattle due to its strong odour and bitter taste. The milk of cows grazing pastures containing significant amounts of Yarrow can become tainted with the strongly aromatic, somewhat unpleasant-smelling volatile oil the plant contains (Frankton & Mulligan 1970). A. millefolium can compete successfully with moderately tall grasses and is often present in species-rich, short-turf vegetation (Sinker et al. 1985).

The established strategy of A. millefolium is categorised as C-S-R, meaning it is a balanced mixture of all three basic plant strategies, Competitor, Stress-tolerator and Ruderal (Grime et al. 1988, 2007).

Variation

A. millefolium s.s. is a component species of a very complex polyploidy species aggregate, A. millefolium s.l., in a series of cytotypes that ranges from diploid to octoploid (Warwick & Black 1982). There is sufficient variation within A. millefolium s.s. for four rather local varieties to be distinguished in B & I by Sell & Murrell (2006), although they appear to have been of insufficient interest for Stace (2019) to mention them. The coastal form of the plant is var. compacta Bréb., which also occurs on mountain cliffs inland (H.J. Killick, in: Stroh et al. 2023).

Flowering reproduction

Reproduction involves both vigorous vegetative spread by means of creeping rhizomes that form clonal patches and longer distance seed diffusion to fresh, open habitats. Yarrow flowers from June to August, with fruiting following from July onwards. Flowering stems are furrowed, slightly woolly and frequently purplish, 40-60 cm tall, each bearing 50 to 100 small, crowded, white or occasionally pink or deep rose-magenta flowerheads, closely arranged in a flat or somewhat domed, terminal, corymbose panicle inflorescence up to 15 cm in diameter. The individual flowerheads are only 4-7 mm diameter and are composed of five (or occasionally six), outer female ray-florets, 2-4 mm long, that surround (5)10-20(-30) bisexual tubular disc-florets in the centre (Hutchinson 1972).

The flowers are self-incompatible, but the inflorescences and their tightly-packed tubular disc flowers containing nectar generally attract a wide range of insect visitors to pollinate them. The achene fruits are grey, glabrous, globose, 1.5-2.0 mm in size, strongly compressed and furnished with a narrow wing (Sell & Murrell 2006). The achenes lack a pappus of any sort, but are produced in huge numbers and, being very small and light, they are readily wind-dispersed (Melderis & Bangerter 1955; Salisbury 1964: Warwick & Black 1982). The average plant produces over 3,000 achenes per year and germination rates of these small, flat propagules are high, in excess of 75% (Salisbury 1964). However, predation of achenes is also significant, so Bostock & Benton (1979) found the mean number of achenes per stem, allowing for predation losses, was 1,660.

The deep-rooting property of the species, together with its rhizomatous habit, makes it difficult to eradicate from gardens and other habitats, especially as the species is resistant to most herbicides (Salisbury 1964; Grime et al. 1988, 2007). The survey of soil seed banks in NW Europe lists 27 records of A. millefolium achenes being considered transient, six records of it being regarded short-term persistent, two studies found it long-term persistent and, in eleven cases, seed was recognised as being present in soil, but could not be assigned to one of the three previous seed bank types (Thompson et al. 1997). The small achenes incorporate well into soil and appear to display a variety of brief and long survival ability, which when taken together with the characteristic high rate of germination, "adapts the species to establishment in open sites of intermittent availability in either time or space" (Bostock 1978).

Fermanagh occurrence

Yarrow is common throughout Fermanagh, having been frequently recorded in 272 tetrads, 51.5% of those in the VC.

British and Irish occurrence

A. millefolium is very common and widespread in both B & I and, indeed, at the hectad level of mapping, it is more or less ubiquitous. Yarrow occurs throughout B & I in a wide range of habitats at all levels from coastal sand-dunes and sea cliffs, to 1,210 m on Ben Lawers, Mid-Perthshire in Scotland (VC 88).

The data for the BSBI Atlas 2020 shows there has been no significant change in its overall distribution since the 1960s, but there has been a decline in frequency in both B & I since the 1930s. A. millefolium is still very widely grown in gardens and it is frequently and widely sown in wild habitats at all levels in so-called 'wildflower seed mixtures'. The seed used in these mixtures is of varying provenance and the Yarrow plants it produces exhibit a wide range of colour and flower variation not normally associated with the native species (H.J. Killick, in: Stroh et al. 2023).

European and world occurrence

A. millefolium belongs to the Eurasian boreo-temperate phytogeographical element and is widely distributed across most of Europe and deep into C Asia. It is less prevalent southwards into the Mediterranean basin, being scarce in the Iberian peninsula, absent from Sicily, Crete, Cyprus, the Greek islands, most of Turkey and all of N Africa (Hultén & Fries 1986, Map 1805). A. millefolium s.s. is introduced in N America, parts of S America, S Australia and New Zealand. The broader A. millefolium s.l. species complex has a circumpolar distribution.

Uses

Yarrow has been a valued medicinal herb in cultivation since ancient times and was used to treat a wide range of ailments of both man and farm animals. Most notably, it was used as a wound-herb to staunch bleeding of both deep cuts and also nosebleeds.

There are at least 17 garden cultivars of either A. millefolium itself, or of its hybrid with a form referred to as A. × 'Taygetea' listed in Royal Horticultural Society Index of garden plants (Griffiths 1994). Some of these cultivated varieties have white flowers and others are double forms, or have red, dark rose, deep burgundy, magenta-red, sunset-red and some yellow, vivid- or bright-pink, pink tinged with purple, dark lavender, purple, or maize-yellow flowers (Griffiths 1994). Magenta coloured flowers are characteristic of cultivated hexaploids, but many pentaploid hybrids are also magenta (Warwick & Black 1982).

Names

The Latin generic name 'Achillea' is derived from the Greek hero Achilles, who in mythology was taught of its healing properties by Chiron the Centaur, and then (according to the Iliad) first used it to heal the wounds of Telephus (Allan 1978; Stearn 1992; Baumann 1993). The Latin specific epithet 'millefolium' means 'a thousand leaves', referring to the many feathery leaf segments.

The plant has many English common names, some of which refer to its medicinal properties and others to its finely cut leaves such as 'Milfoil', a mere anglicised form of its Latin species name (Grigson 1955, 1987).

The familiar name 'Yarrow' derives from the Old English 'yarowe', in The Grete Herball of 1526 (Ryden 1984), or alternatively from the Anglo-Saxon 'gearwe' (Grigson 1974). The Grete Herball is the first illustrated herbal published in English anonymously by Peter Treveris in 1526. It is essentially a translation of another anonymous French herbal, Le Grant Herbier, itself compiled from several sources, including one called Circa Instans dating from around 1150 (Anderson 1977; Ryden 1984).

Prior (1879) somehow links 'yarowe' or 'gearwe' with 'Vervain', the 'hierabotane', or the 'gerebotanon' of the early herbalist Apuleius, a name itself derived from the Greek, 'iepa botavn', or 'holy herb', so-called for its wound-healing property. The initial 'hi' of Greek words has in the Germanic languages usually been replaced with a 'y' or 'j', and thus 'Hiera' has become 'Yarrow' (Prior 1879).

Threats

None.

References

Grime, J.P., Hodgson, J.G. and Hunt, R. (1988, 2007), Allan, M. (1978); Baumann, H. (1993); Stearn, W.T. (1992); Warwick, S.I and Black, L. (1982); Prior, R.C.A. (1879); Grigson, G. (1955, 1987); Grigson, G. (1974); Ryden, M. (1984); Griffiths 1994; Hultén & Fries 1986; Stroh et al. 2023; Bostock 1978; Bostock and Benton (1979); Salisbury 1964; Melderis & Bangerter 1955; Sell & Murrell 2006; Stace (2019); Sinker et al. 1985; Hutchinson 1972; Frankton & Mulligan 1970; Thompson et al. 1997;Prior 1879; The Iliad, Garrard & Streeter 1983; The Grete Herball; Anderson 1977.