Achillea millefolium (2022)

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infestation (Photo: Trevor James)habit (Photo: Sheldon Navie)lower leaves innumerous basal rosettes (Photo: Sheldon Navie)creeping underground stem (Photo: Trevor James)close-up of a finely-divided leaf (Photo: Trevor James)ribbed hairy stem and smaller upper leaves (Photo: Sheldon Navie)white flower-heads in a slightly-rounded dense cluster (Photo: Sheldon Navie)pink flower-heads (Photo: Sheldon Navie)close-up ofthe small flower-heads (Photo: Sheldon Navie)old flower-heads (Photo: Sheldon Navie)close-up of seeds (Photo: Steve Hurstat USDA PLANTS Database)young plant (Photo: Trevor James)a modern hybrid cultivar with orange flowers (Photo: Sheldon Navie)

Achillea millefolium

Achillea millefoliumL.

Asteraceae (Queensland, New South Wales, the ACT, Victoria, Tasmania, Western Australia and the Northern Territory)Compositae (South Australia)

bad man's plaything, bloodwort, carpenter's weed, common yarrow, devil's nettle, devil's plaything, fernweed, knight's milfoil, milfoil, nose bleed, nosebleed, old man's pepper, sanguinary, soldier's woundwort, staunchweed, thousand leaf, thousand seal, thousand weed, thousnad-leaf, thousandleaf, woundwort, yarrow, yarrow bloodwort, yarrow milfoil, yarroway

Nativeto Eurasia, including most of Europe andmany parts of Asia (i.e. from Turkey eastwards toSiberia and north-western India).

Note: Several closely-related plants from Northern America, that were regarded as separate species, are now recognised as sub-species of yarrow (Achillea millefolium) by some botanists. Under this classification system theplantthat is native toEurasia, andthe onethat has been introduced intoAustralia,is called Achillea millefolium subsp. millefolium. Itis generally considered to be introduced to North America.

Yarrow (Achillea millefolium) was originally brought from Europe to be planted in herb gardens. It has had a long-standing reputation for healing wounds andalso has a number of other medicinal uses. It it also a favoured plant in English cottage-style gardens, from whichit has escaped. In addition to the regular white and pink flowered forms of this species, several other cultivars arealso still commonly grown in the temperate regions of Australia including 'Cerise Queen', 'Fanal', 'Red Beauty', 'Paprika', 'Rosea' and 'Apfelblute'.

In more recent times a wide variety of hybrid cultivars, displaying a wider range offlower colours, have also been developed (e.g.'Great Expectations', 'Moonshine','Lachsschonheit' or 'Salmon Beauty', 'Schwellenberg' and 'Taygetea'). Most of these have yarrow (Achillea millefolium) as one of the parents, but arethought to beless invasive than the original species.

This species is widely naturalised in southern and eastern Australia, and is particularly common in temperate and cooler highland areas. It has been recorded from south-eastern Queensland,eastern New South Wales, the ACT, Victoria, Tasmania,south-eastern South Australia andthe southern parts of Western Australia.

Yarrow (Achillea millefolium)is probably most widespread in Victoria, where it ispresent in all but the drier parts in the north-west of the state. Itismost common in highland areas, and particularly common in thesub-alpine areas in the north-east of Victoria. In New South Wales it is generally found inthe eastern parts of the statesouth from Lismore, and is once again most common in highland regions (i.e. on the northern, central and southern tablelands - including the ACT). It is also quite common and widespread in Tasmania, particularly inwell settled and agricultural areas in the north and east of the state. In South Australia it is well established in the south-eastern parts of the state and is possibly also naturalised in the Northern Lofty Ranges region and on the Eyre Peninsula. In Western Australia there are only scattered occurrences of this species near inhabited areas in the southern and south-western partsof the state (i.e. in the Perth, Pemberton and Esperance districts). It has also been recorded as locally naturalisedaround Stanthorpe in the cooler highland areas of south-eastern Queensland.

Yarrow (Achillea millefolium)is also naturalised in many other parts of the world, including North America and New Zealand.

This species usually grows in disturbed habitats, neglected gardens, waste areas, pastures, turfed areas, gullies and along roadsides in relatively moist locations within the temperate regions of Australia. It is particularly common in highland areas and is occasionally also found in the cooler highland parts of sub-tropical regions. In addition to these habitats, yarrow (Achillea millefolium) has become well established in native grasslands and woodlands, particularly in the sub-alpine areas of south-eastern Australia.

In New Zealand it is common in disturbed sites and waste areas (e.g. railways and industrial areas), along roadsides, in pastures and in lawns. It is also found in marshy sites, in coastal environs, and forms extensive patches in cultivation and grasslands. In its native habitat in Eurasia, yarrow (Achillea millefolium) generally grows in meadows and pastures on all but the poorest of soils.

Along-lived (i.e. perennial), mat-forming, herbaceous plantthat developsan extensive network of branching underground stems (i.e. rhizomes). Numerous short-lived upright (i.e. erect or ascending) stems usually growing 10-60 cm tall, but occasionally reaching up to 1 m in height,areproduced each year.

  • a long-lived plantproducingseveral short-lived stems each year from a network of creeping underground stems.
  • plants produce arosette of shortly-stalkedleaves followed by uprightstems with smaller, stalklessleaves.
  • its elongated leaveshave a ferny appearance, being highly divided into numerous tinynarrow segments.
  • its flower-headshave about fivewhite, pink or mauve'petals'and are borne inlarge flat-topped or slightly rounded clustersat the tips of the stems.
  • several smallhairless 'seeds'are produced in each of the mature flower-heads.

Seedlings havetwo seed-leaves (i.e. cotyledons) that are egg-shaped (i.e. ovate), oblong or club-shaped (i.e. clavate) in outline and relatively small (2-4 mm long and 1.5-2 mm wide). The first true leaves appear to be oppositely arranged and are usually slightly three-lobed with a scattered covering ofhairs on their upper surfaces.The followingleaves areprogressively more deeply lobed and quickly become divided into numerous narrow (i.e. linear) segments. Young plants initially form a loose basal rosette of leaves.

What can appear to be a group of young plants, may in fact be a collection of shoots being produced froma network of creeping underground stems (i.e. rhizomes). These 'seedlings' are not true seedlings andwill not have any seed-leaves (i.e. cotyledons).

The stems are generally unbranched, except in the dense flower clusters,and are almost rounded in cross-section (i.e. terete). They are finely ridged (i.e.striate) and usually at least partially covered in soft, woolly hairs (i.e. pubescent).

The soft and feathery-looking leaves are initiallycrowdedinto a loose basal rosette andarealternately arranged along the upright (i.e. erect) stems.The lowermost leaves(i.e. the basal leaves), and those near the base of the stem, are usually shortly-stalked (i.e. petiolate) and somewhat larger in size (5-15 cm long and 2-5 cm wide). While the leaves along the remainder of the stem (i.e.the cauline leaves) are usually stalkless (i.e. sessile),and tend todecrease in size (2-10 cm long and 8-25 mm wide)and become less divided towards thetops of the stems.Leaves are generally elongatedinoutline(i.e. lanceolate, narrowly elliptic or narrowly ovate) andhighly divided into numerous tiny narrowsegments (i.e.2- or 3-pinnatisect), the final segmentsranging from 0.2-1 mm wide. However, they are divided practically to the main leaf branch (i.e. rachis), which is very thin (0.4-1.5 mm wide),and so appear to be compound (i.e. bipinnate) with numerous (about 15) pairs of leaf branchlets (i.e. pinnae) each about 5-20 mm long.Leaves are usually softly hairy (i.e. pubescent), particularly when young. They alsogive off a strong scent, particularlywhen damaged (i.e. they are aromatic).

The flowers are actually small flower-heads (i.e. capitula) that are made up of numerous tiny flowers (i.e. florets)borne on theexpanded top of a flower stalk (i.e.receptacle) andsurrounded by several rows of bracts that form a cup-like structure (i.e.an involucre).About 20bracts (i.e. involucral bracts) surround each flower-head(i.e. capitulum) andare arranged in 3-4 indistinct overlapping rows. These bractsvary in size (from 1-5 mm long), are relatively hairy,and are somewhat elongated in shape (i.e. narrowly ovate). Theyare greenish in colour,oftenwithdarker margins, andturn pale brownas the flower-heads mature. Each flower-head (5-10 mm across) usually has five 'petals' (occasionally 4-7) that are white, pink, reddish-pink or mauve in colour. They arequite small(1-4 mm long and about 3 mm wide), usually have threetiny teeth at their tips, andare actually the upper parts oftiny female flowers (i.e. the ligules ofray florets). At the centre of each flower-headare numerous (10-20) tiny tubular flowers about 2 mm long (i.e.discor tubular florets). They are yellow, white or cream in colour withfive small teeth towards their tips. Thesetubular florets haveboth male and female flower parts (i.e. they are bisexual).

Large numbers of the flower-headsare densely arrangedinto flat-topped or slightly rounded branched clusters at the tips of the stems (i.e. in terminal corymbs). These flower-head clusters can be up to 15 cm across, but are usually4-10 cm across. Each individual flower-head (i.e. capitulum)is borne on a shortleafless stalk (i.e. peduncle) 1-5 mm long, with thestalksof the outermost flower-heads (i.e. capitula) generally being longer than those of the inner ones. Flowering occurs during summer and autumn (i.e. from December to May) in the southern parts of the country, butusually occursin spring (i.e. from September to November) in warmer regions. The'seeds' (i.e.achenes)are elongated in shape (1.4-2.5 mm long and0.5-0.8 mm wide) and somewhat flattened (about 0.3 mm thick). They are greyish or dark brown in colour, hairless (i.. glabrous),smooth in texture, and have a slightly glossy appearance. The mature'seeds' are not topped with any structures (i.e. they do not have a pappus).

This species reproduces by seed, and also vegetatively by creeping undergroundstems (i.e. rhizomes) which give rise to new shoots. Its seeds are long-lived and may remain dormant in the soil for many years.

The tiny seeds areprimarily wind-dispersed,but are usually only blown short distances. Plants may also spread short distances laterally over time, via their creeping underground stems (i.e. rhizomes), and can form quite large colonies. The seeds and rhizomes may also be dispersed in dumped garden waste. In addition,rhizome segments (that are each capable of developing into new plants) may be spread in contaminated soil during road maintenance, cultivation, and other activites that involve the movement of soil.It is also highly likely that the tiny seeds are spread on clothing and vehicles. Yarrow (Achillea millefolium) seeds have also often beenfoundto contaminatecommercial seed in other countries.

Yarrow (Achillea millefolium) is regarded as an environmental weed in Victoria,the ACT, andthe southern parts of New South Wales. Though this species isnaturalised inmany parts of southern Australia, it isonly considered to be a serious problem in the alpine and highland regions of south-eastern Australia. However, within these regions it is ofrelatively high importance and it isregarded by some to bethe most concerning environmental weed in the Australian Alps.

Yarrow (Achillea millefolium) allocates a relatively large proportionof resources to below-ground structures (i.e. rhizomes),and this is thought to be the reason why it is such astrong competitorat higher altitudes (i.e. where snow and cold temperatures can prevent growth of plants for much of the year). This species has been naturalised in the Australian Alps for many years (i.e. as a sleeper weed),but its population rapidly increased during the 1990's.Apopulation increase that isthought to be partly due to the use of gravel from contaminated pitsin road maintenance activities and/or the use ofcontaminated hayin rehabilitation works. It is now considered to behighly invasiveandquite vigorous innative vegetation in highland areasandis a regarded as a potential threat to the native sub-alpine and alpine plant communities of the Australian Alps.

This speciesisof particular concern in and around ski resorts in southern New South Wales and isasignificant environmental weed in the Kosciuszko National Park, near the New South Wales/Victoria border. In the Kosciuszko National Park it is primarily found along roadsides (including drains, culverts and embankments), near tracks, and around buildings and ski lodges.However, it is spreading from these sites into the surrounding natural vegetation. It isalso present further north in the Brindabella National Park, and inthe ACT it is of concern in the Ginini Flats Wetlands Ramsar Site. Here yarrow (Achillea millefolium) is growingalong the Mt. Franklin road, from where it has the potential to spread into the nearby wetlands and surrounding flats. It is also present in similar situations in the north-eastern parts of Victoria, whereit is listed as an environmental weed in the Goulburn Broken Catchment regionand has been recorded fromthe resort areas at the Mt Buller and Mt Stirling alpine resorts.

Yarrow (Achillea millefolium)also forms significant weedy infestations in Tasmania, but here it is generally seen as a weed of roadsides, turf and pasture areas. It it relatively widespread and common, particularly in agricutrural areas the north-east (e.g. in the Tamar Valley) and insettled areas around Hobart in the south-east (e.g. in thebushland areasfringing the Derwent River). However, it is a potential weed ofsome significant sub-alpine and alpineareas in the western parts of Tasmania.Because it generally grows on wasteland and road verges in the southern parts of Western Australia, andin similar habitats in the south-eastern parts of South Australia and Queensland, it has a relatively limited environmental impact in these states.

Apart from being an environmental weed, this speciescan be weedy in other situations (e.g. in gardens, lawns and pastures). Because of its spreading underground stems (i.e. rhizomes) is can be very difficult to remove from gardens and turfed areas. Dairy cattle which eat itare also reported to produce tainted milk.

Yarrow (Achillea millefolium) is not declared or considered noxious by any state or territory government in Australia.

For information on the management of this species see the following resources:

Yarrow (Achillea millefolium) issimilar to tansyleaf milfoil (Achillea distans subsp. tanacetifolia) and fernleaf yarrow (Achillea filipendulina), closely related species that have also become naturalised in Australia. Tansyleaf milfoil (Achillea distans subsp. tanacetifolia) is particularly similarandintermediates between these two speciesare also known to occur. These speciesmay be distinguished by the following differences:

  • yarrow (Achillea millefolium) has leaves that are divided almost all the way to the midrib (i.e.rachis), into very narrow segmentsthat have asparse to densecovering ofsoft spreading hairs. The wings on either side of the midrib arealmost non-existent(less than 1 mm wide) and are usually straight betweeneach of the leafsegments (i.e.pinnae). Naturalised forms generally have white, pink, reddish-pinkor mauve coloured flowers.
  • tansyleaf milfoil (Achillea distans subsp. tanacetifolia) has leaves that are divided most of the way to the midrib (i.e. rachis), into very narrow segments and have asparse to densecovering ofsoft spreading hairs. The wings on either side of the midribare relatively broad (1-2 mm wide) and are usuallytoothed or lobed between each of the leafsegments (i.e. pinnae). Naturalised forms generally have white, pink, reddish-pinkor mauve coloured flowers.
  • fernleaf yarrow (Achillea filipendulina) has leaves that are dividedmost ofthe way to the midrib (i.e.rachis) into relatively broad toothed segments and have a dense covering of short close-lying (i.e. appressed) hairs. The wings on either side of the midrib (i.e. rachis) arerelatively broad (1-2 mm wide) and are usuallytoothed or lobed between each of the leafsegments (i.e.pinnae). Naturalised forms generally havegolden yellow flowers.

In addition, the leaves and habit ofyoung fennel (Foeniculum vulgare) plants are very similar. However, fennel (Foeniculum vulgare) leavesare generally larger (30-50 cm long) and hairless (i.e. glabrous). Mature plants easily distinguished by theirmuch larger (1.5-2 m tall) habit,thick woody stems,and compound clusters of small yellow flowers.

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