Achillea millefolium
(yarrow)

Pictures

Identity

Preferred Scientific Name

• Achillea millefolium L.

Preferred Common Name

• yarrow

Other Scientific Names

• Achillea albida Willd.
• Achillea ambigua Boiss.
• Achillea angustissima Rydb.
• Achillea arenicola A.Heller
• Achillea bicolor Wender.
• Achillea borealis Bong.
• Achillea californica Pollard
• Achillea ceretanica Sennen
• Achillea compacta Lam.
• Achillea coronopifolia Willd.
• Achillea crassifola Colla
• Achillea cristata hort. ex DC.
• Achillea dentifera Rchb.
• Achillea eradiata Piper
• Achillea fusca Rydb.
• Achillea gigantea Pollard
• Achillea gracilis Raf.
• Achillea haebkeana Tausch
• Achillea intermedia Schleich.
• Achillea lanata Lam.
• Achillea lanulosa Nutt.
• Achillea laxiflora A.Nelson
• Achillea magna Auct.
• Achillea magna L.
• Achillea marginata Turcz. ex Ledeb.
• Achillea megacephala Raup
• Achillea nabelekii Heimeri
• Achillea occidentalis Raf. ex Rydb.
• Achillea ochroleuca Eichw.
• Achillea ossica K.Koch.
• Achillea pacifica Rydb.
• Achillea palmeri Rydb.
• Achillea pectin-veneris Pollard
• Achillea pratensis Saukel and R.Länger
• Achillea pseudo-tanacetifolia Wierzb. ex Rchb.
• Achillea puberula Rydb.
• Achillea pumila Schur
• Achillea rosea Desf.
• Achillea setacea Schwein.
• Achillea sordida (W.D.J.Koch) Dalla Torre and Sarnth.
• Achillea subalpina Greene
• Achillea submillefolium Klokov and Krytzka
• Achillea sylvatica Becker
• Achillea tanacetifolia Mill.
• Achillea tenuis Schur
• Achillea virgata hort. ex DC.
• Achillios millefoliatus St.-Lag.
• Alitubus millefolium (L.) Dulac
• Alitubus tomentosus Dulac
• Chamaemelum millefolium (L.) E.H.L. Krause
• Chamaemelum tanacetifolium (All.) E.H.L.Krause

International Common Names

• English: bloodwort; carpenter’s weed; common yarrow; milfoil
• Spanish: falsa Altamisa; hierba de las cortaduras; milefólio; milenrama; milhojas; plumajillo
• French: achillée millefeuille; aillefeuille; herbe-à-dinde
• Chinese: shi
• Portuguese: erva-carpinteira; erva-das-cortadelas; erva-de-João-de-Grisley; espuma-do-mar; eupatório-demésue; macela; macela-de-São-João; macela-Francesa; milefólio; mil-em-rama; milfolhada

Local Common Names

• Bolivia: salvia de virgen
• Cuba: milenrama
• Dominican Republic: ciprés de invierno; ciprés de Judea; ciprés de perla; milfoil; perla; sereno de invierno
• Germany: Gemeine Schafgarbe
• Guatemala: alhucema; mil en rama; pumajillo
• Haiti: mil en rama
• Honduras: alhucema; mil en rama; talquezal
• Italy: millefoglio
• Jamaica: milfoil
• Japan: seiyonokogiriso
• Mexico: mil en rama
• Netherlands: Duizendblad
• Puerto Rico: milfoil; perla
• Sweden: roellika
• USA: milfoil; nose-bleed; plumajillo; sanguinary; soldier's woundwort; thousand leaf; thousand seal; western yarrow

EPPO code

• ACHMI (Achillea millefolium)

Summary of Invasiveness

A. millefolium is an erect, herbaceous perennial plant native to temperate regions. It has a wide native range; growing well in almost any kind of soil and temperature (PROTA, 2015). Its ability to spread through the rhizome, long term dormancy and prolific seed production are key for the species being a successful colonizer and invader (Bostock, 1978; Kannangara and Field, 1985a; Bourdot and Field, 1988; Sanecki et al., 2003). One of the oldest known plants used by humans with records dating to 65,000 B.P., it is cultivated for its medicinal properties and as an ornamental (Mitich, 1990; Applequist and Moerman, 2011). Although common and widespread, it is reported as problematic only in a few countries in its native range (Sweden, Finland and Norway) (Mitich, 1990). It has been planted outside its native range for site improvement, as an ornamental and for its medicinal properties. It has been recognized as an invasive plant in some countries, such as New Zealand, Australia, Chile, and Argentina (Bourdot et al., 1979; Bourdot and Field, 1988; Sanecki et al., 2003; Barros and Pickering, 2014).

Taxonomic Tree

• Domain: Eukaryota
•     Kingdom: Plantae
•         Phylum: Spermatophyta
•             Subphylum: Angiospermae
•                 Class: Dicotyledonae
•                     Order: Asterales
•                         Family: Asteraceae
•                             Genus: Achillea
•                                 Species: Achillea millefolium

Notes on Taxonomy and Nomenclature

The genus Achillea, has ca. 110– 140 species, mostly native to Eurasia, with a few native to northern Africa and North America. The name Achillea refers to Achilles using the species to treat the wounds of his fellow soldiers during the Trojan War; the ephithet millefolium is a reference to its “many leaves” or “thousand leaves” (Mitich, 1990). The origin of the common name “yarrow” is unknown, but it is believed to come from “garawa” and to have been in use since ca.725 A.D. (Mitich, 1990).

Hybridization and polyploidism is common in Achillea millefolium, which has made the delimitation of the species difficult, making several closely related species treated as either belonging to an A. millefolium species complex or as a single species with multiple varieties (Gou et al., 2005; Applequist and Moerman, 2011). The species lacks reproductive isolation between the ploidy populations and good defining morphological characters to differentiate the ecotypes into species (Tyrl, 1975).

There is no consensus as whether the North American populations, with about 58 names applied, should be treated as conspecific with A. millefolium, or as different species (Flora of North America Editorial Committee, 2015). Native Americans used the indigenous taxon in the pre-Columbian era, but later uses probably also included plants introduced from Europe (Guo et al., 2005).

Ramsey et al. (2007) assessed the history of differentiation of A. millefolium using molecular techniques and their results suggest that the species in North America is a monophyletic group distinct from the European and Asian relatives, validating the colonization of the species via the Bering Land Bridge in the Pleistocene. The authors recommend the recognition of two species in North America: A. borealis for the autopolyploid members of A. millefolium that occur from Canada to Mexico, and A. alpina for the allotetraploids that occur mainly in Asia but extend to Canada and Alaska. This Compendium follows The Plant List (2013) and the use of Achillea millefolium, until changes are accepted and widely implemented. 

Description

The following description is from Flora of North America Editorial Committee, 2015:

Perennials, 6–65+ cm (usually rhizomatous, sometimes stoloniferous). Stems 1(–4), erect, simple or branched, densely lanate-tomentose to glabrate. Leaves petiolate (proximally) or sessile (distally, weakly clasping and gradually reduced); blades oblong or lanceolate, 3.5–35+ cm × 5–35 mm, 1–2-pinnately lobed (ultimate lobes ± lanceolate, often arrayed in multiple planes), faces glabrate to sparsely tomentose or densely lanate. Heads 10–100+, in simple or compound, corymbiform arrays. Phyllaries 20–30 in ± 3 series, (light green, midribs dark green to yellowish, margins green to light or dark brown) ovate to lanceolate, abaxial faces tomentose. Receptacles convex; paleae lanceolate, 1.5–4 mm. Ray florets (3–)5–8, pistillate, fertile; corollas white or light pink to deep purple, laminae 1.5–3 × 1.5–3 mm. Disc florets 10–20; corollas white to grayish white, 2–4.5 mm. Cypselae 1–2 mm (margins broadly winged).

Distribution

A. millefolium has a wide distribution, which is partly due to its complex taxonomy and treating all populations within an “A. millefolium complex” (PROTA, 2015). It is considered as native to Eurasia and North America and found primarily throughout the temperate and boreal zones of the Northern Hemisphere and, to a lesser extent, in the Southern Hemisphere (PROTA, 2015). As a native, it is widely distributed in North America, Central America, Asia and Europe. Reported as introduced for Bhutan, China (widely cultivated and naturalized), Japan, Australasia, and parts of Africa and South America (see Distribution Table for details).

Distribution Table

The distribution in this summary table is based on all the information available. When several references are cited, they may give conflicting information on the status. Further details may be available for individual references in the Distribution Table Details section which can be selected by going to Generate Report.

History of Introduction and Spread

There is scarce information on the introduction of A. millefolium and its spread outside its native range. It is one of the oldest plants with evidence of human use, and diversification apparently occurred in southeastern Europe and southwestern Asia (Mitich, 1990; Gou et al., 2005). Although it is reported to have been used by Native Americans prior to colonization by Europeans, the species was also introduced from Europe (Guo et al., 2005). Most of the information available for its introduction is from New Zealand, where it was introduced in the late 1800’s to establish pastures on cleared lands, for medicinal purposes and as forage for sheep (Bourdot et al., 1979; Bourdot and Field, 1988). It was also introduced in Australia as an ornamental plant and for medicinal uses (Sanecki et al., 2003). In both countries it is reported to have spread considerably. In New Zealand, the species was included in pasture seed mixtures, which contributed to its dispersion (Bourdot et al., 1985).

Introductions

Risk of Introduction

A. millefolium is a successful colonizer due to its long-term dormancy, prolific seed production and wind dispersal of seeds, and asexual reproduction through its rhizomes (Bostock, 1978; Kannangara and Field, 1985a; Bourdot and Field, 1988; Sanecki et al., 2003). It has a broad distribution and can grow in a wide variety of habitats and altitude up to 3,600 m (PROTA, 2015). It is widely cultivated for medicinal and ornamental purposes, and sold at nurseries and internet sites locally and internationally (Mitich, 2005). At some of the internet sites where it is sold, a warning is issued that it could escape from cultivation, and becoming weedy or invasive in adjacent areas if not managed. Its rhizomes are also reported as difficult to eradicate (Bourdot and Field, 1988). All of the above contribute to its spread and give the species a high risk of dispersing outside its native range or managed areas. 

Habitat

A. millefolium is a common widespread plant that is also cultivated for its flowers and for medicinal purposes. It has a very broad and diverse ecological amplitude, and is a frequent colonizer of disturbed areas. The species can grow from sea level to alpine areas (ca. 0-3600m) and in a variety of habitats. Habitats include mesic to dry prairies, pastures, meadows, woodlands, stream banks, fallow fields, grassy waste areas, and edges of paths, yards, or hedges. Found in dry or sandy soils, also in damp, clayey, and salty soils (Mitich, 1990; Flora of North America Editorial Committee, 2015; PROTA, 2015). It is also one of the understory species in boreal forests, able to grow on cold soils with low levels of nutrients and moisture (Turkington et al., 2002). Vervuren et al. (2003) report the species to be flood intolerant, which limits its distribution along riparian forests subjected to floods.

North American populations are adapted to coastal habitats, salt marshes, forests, steppes and alpine meadows. The European and Asian populations are geographically more widespread but mostly restricted to grasslands and forest margins (Ramsey et al., 2007). 

Habitat List

Biology and Ecology

Genetics

The chromosome number reported for A. millefolium varies; 2n= 18, 27, 36, 45, 54, 63, 72 (including counts from Europe) (Flora of North America Editorial Committee, 2015).

Reproductive Biology

A. millefolium has two growth forms, one forming rosettes which reproduce asexually through the rhizomes and the other erect sexually reproducing plants (Grainger and Turkington, 2013). The species is self-incompatible (Bourdot and Field, 1988; Vetter et al., 1996; Lofgren, 2002) and is visited by a great array of pollinators (Bourdot and Field, 1988; Foster, 1988).

Physiology and Phenology

A. millefolium has an underground storage rhizome, a prolonged flowering season, a high seed production and long term dormancy (Bostock, 1978; Bourdot and Field, 1988; Sanecki et al., 2003). A photoperiod of between 12 and 16 hours, temperature and irradiance all have an influence over flowering (Zhang et al., 1996). Seeds are produced during summer and autumn; germination spreads over months up into spring, some occurring right after fruiting, except in colder months (Bostock, 1978; Bourdot and Field, 1988). Shading has a negative impact on seed production (Bourdot and Field, 1988). Seedling rapid growth and the high regenerative capacity of the rhizomes promote the formation of monocultures along disturbed habitats (Bourdot and Field, 1988; Sanecki et al., 2003). Most of the rhizomes are in the top 50 mm of soil and will form plants when exposed (Bourdot and Field, 1988).

Plants at high latitudes or high elevations have darker coloured margins on the phyllaries. At high latitudes, elevations, or from extreme desert locations populations are more densely lanate than in less extreme habitats (Flora of North America Editorial Committee, 2015). An increase in the below-ground biomass allocation with an increase in altitude is reported (Johnston and Pickering, 2004).

Activity Patterns

The high production of seeds during summer and autumn, their dormancy, and survival when buried in soil contribute to the species reproductive success (Kannangara and Field, 1985a). Seeds need light stimulus for germination (Kannangara and Field, 1985b). The viability of the seeds is over 90% with a germination rate of 41% after nine years of dry storage and 44% of germination after four years in the soil (Bourdot, 1984). Reported by Kannangara and Field (1985a) is that seeds on the top 8 cm of soil may completely lose viability within a two year period, while those buried deeper will remain viable longer. Germination is best at 15-30°C (Zarganhi et al., 2014). When comparing the germination patterns of A. millefolium in a native area (Germany) and an invaded one (New Zealand), Beckmann et al. (2011) found that maximum germination was higher in the invasive populations with warmer temperatures, resulting in a greater establishment rates for this species in these areas. Also compared to the native range, the species performs better in invaded areas due to an increase in vegetative reproduction (Beckmann et al., 2009).

A. millefolium seeds are reported to be poor competitors (Greiling and Kichanan, 2002; Lamb and Cahill, 2006). The species is a poor competitor when seedlings are grown with competing neighbours; as seen with Dactylis glomerata and Vicia cracca. Fertilizers do not affect the competitive response of A. millefolium (Gurevitch et al., 1990).

Nutrition

Despite the fact that seeds and seedlings are poor competitors, even with the addition of fertilizers (Gurevitch et al., 1990), an increase in soil nutrients, such as nitrogen, results in an increase of biomass allocation into reproduction, increasing the probability of flowering in A. millefolium and providing a competitive advantage over species that reproduce mainly vegetatively (Grainger and Turkington, 2013).  

Associations

In Denmark, there is evidence of a positive adaptation of A. millefolium to terpenes in the soil produced by Thymus pulegioides and T. serpyllum, suggesting a local association in this community (Grondahl and Ehlers, 2008).

Environmental Requirements

A. millefolium is highly adaptable and tolerates a wide range of environments; it can grow well in a broad range of soils, elevations and climates. It is also drought and frost resistant, adapting well to alpine habitats (Sanecki et al., 2003). A. millefollium is tolerant to shading (Bourdot et al., 1984) and to saline water irrigation, up to 4 dS m^–1 (Niu and Rodríguez, 2006). Studies suggest that A. millefolium is sensitive to O_3, which causes physiological damage and visible leaf damage (Scebba et al., 2006).

Although the species can tolerate several frosts, plants respond better to temperatures of over 10°C and moderate to high light levels (Bourdot and Field, 1988). Johnston and Pickering (2005) report that with an increase in temperature due to climate change, the species could flower earlier with a longer flowering period, producing more seeds as a consequence.

Climate

Air Temperature

Rainfall Regime

Soil Tolerances

Soil drainage

• free

Soil reaction

• acid
• alkaline
• neutral
• very alkaline

Soil texture

• heavy
• light
• medium

Special soil tolerances

• infertile

Natural enemies

Means of Movement and Dispersal

Vegetative reproduction occurs via the rhizomes mainly when they get fragmented and apical dominance is removed (Bourdot, 1984; Bourdot et al., 1985). Seeds are dispersed by wind over short distances of 2-3 metres (Bourdot and Field, 1988). They are also reported to be dispersed by clothing, vehicles and pack animals (Barros and Pickering, 2014).

A. millefolium is reported to be intentionally introduced to South Chile and to the Aconcagua Park in Argentina (Barros and Pickering, 2014). The cultivar ‘GO152’ was produced at AgResearch Grasslands at New Zealand to be available to farmers and researchers for forage use (Rumball, 2005). Intentionally introduced to New Zealand and Australia for pasture regeneration, as a medicinal plant, for forage and as an ornamental (Bourdot et al.; 1979; Bourdot and Field, 1988; Sanecki et al., 2003). 

Pathway Causes

Pathway Vectors

Impact Summary

Economic Impact

In New Zealand, crop losses have been attributed to A. millefolium, where cost of manually removing the species is reported to be very high (Bourdot and Field, 1988). Dairy products from cows feeding on A. millefolium have an undesirable flavour (Mitich, 1990). 

Environmental Impact

A. millefolium has an extensive rhizome system which gives the species a strong competitive advantage over native ones. In controlled experiments, the A. millefolium rhizome system restricted the growth of Poa fawcettiae, which is a dominant species in the Australian Alps (Johnston and Pickering, 2004).

Social Impact

Plants contain possible allergens that could cause allergic reactions (Warwick and Black, 1982).

Risk and Impact Factors

• Invasive in its native range
• Proved invasive outside its native range
• Has a broad native range
• Abundant in its native range
• Highly adaptable to different environments
• Is a habitat generalist
• Pioneering in disturbed areas
• Tolerant of shade
• Fast growing
• Has high reproductive potential
• Gregarious
• Has propagules that can remain viable for more than one year
• Reproduces asexually

• Monoculture formation
• Negatively impacts agriculture
• Threat to/ loss of native species

• Hybridization
• Rapid growth
• Rooting

• Highly likely to be transported internationally deliberately
• Difficult/costly to control

Uses

Economic Value

A. millefolium is one of the oldest plants known to have been used for traditional medicine, and is still in use worldwide (Mitich, 1990; Applequist and Moerman 2011). Some of the uses reported are for gastrointestinal disorders, bleeding, pain, wounds, anxiety disorders, skin conditions and inflammation. Biomedical research findings have validated some of these medicinal uses (Applequist and Moerman, 2011; Dall’Acqua et al., 2011; Baretta et al., 2012; Akram, 2013; Souza et al., 2013; Soukand and Kalle, 2013; Miranzadeh et al., 2015). Yarrow extract is listed as an ingredient in about 1998 cosmetic products (Cosmetic Ingredient Review, 2001). Extracts from the aerial parts are also used as a veterinary treatment for ear infections (Lans, 2008).

Hybrids and cultivars have been developed from various Achillea species, including A. millefolium, which is considered as an important garden plant (Zhang et al., 1996). Armitage (1992) report four to five species of Achillea that are commonly produced in American and European nurseries to use as garden plants and as a cut flower.

Social Benefit

A. millefolium is one of the species used in Poland for Assumption Day herbal bouquets, which are composed of medicinal, apotropaic and crop plants to ensure the well-being of farms and the communities (Luczaj, 2011).

Environmental Services

Pecetti et al. (2014) report the species as used for restoration on disturbed Alpine areas; for which they suggest to produce the seeds on lower land, which does not affect either the seed yield or the morphological and physiological characters. This understory herb is part of the primary food source of grazing animals during the snow free season, like the snowshoe hare (Lepus americanus) (Hicks and Turkington, 2000; Turkington et al., 2002). A. millefolium is also recommended to be used for restoration of grasslands to improve the species diversity of habitats (Hopkins et al., 1999).

A. millefolium has been suggested as a species to be planted as part of the cover crop mixture used in apple orchards to attract beneficial arthropods and act as a biocontrol (Bostanian et al., 2004). This was also tested by Bone et al. (2009) without conclusive results for an impact on the arthropod population, suggesting that this strategy might not be suitable for all environments. It is also one of the species recommended to be used as wildflower sod mixtures to be planted in the southeastern USA for low maintenance of sites, land restoration and erosion control (Johnson and Withwell, 1997).

Extracts and essential oils show acaricidal and insecticidal activities and mosquito repellent activity (Jaenson et al., 2006; Song et al., 2016). Benelli et al. (2015) report that the essential oils of A. millefolium show good toxicity rates against the West Nile vector Culex pipiens and the Echinostoma intermediate host, Physella acuta, proposing that further studies should be made to develop vector controls. 

Uses List

Animal feed, fodder, forage

• Forage

Drugs, stimulants, social uses

• Religious
• Smoking

Environmental

• Erosion control or dune stabilization
• Landscape improvement
• Revegetation

General

• Botanical garden/zoo
• Ornamental
• Sociocultural value

Human food and beverage

• Food additive
• Leaves (for beverage)
• Spices and culinary herbs

Materials

• Chemicals
• Cosmetics
• Essential oils
• Pesticide

Medicinal, pharmaceutical

• Traditional/folklore
• Veterinary

Ornamental

• Cut flower
• Potted plant
• Seed trade

Similarities to Other Species/Conditions

A. millefolium s.l. is similar to A. ptarmica L. and A. sibirica Ledeb. The reported differences are that A. millefolium has pinnately-dissected leaves and narrow rachis; and the leaves of the two other species are subentire, serrate or incised, never pinnatifid (Warwick and Black, 1982). Reported also to be similar to Achillea distants subsp. tanacetifolia and A. filipendulina, all introduced to Australia. Hybrids between Achillea distants subsp. tanacetifolia and A. millefolium are reported to occur. Vegetatively it has been confused with fennel (Foeniculum vulgare) (Weeds of Australia, 2015).  

Prevention and Control

Physical/Mechanical Control

Rhizomes of A. millefolium are difficult to kill. Bourdot and Field (1988) recommend that the rhizomes be severely fragmented and then buried in the soil at depths of at least 200 mm. Bourdot (1984) also recommends that after burial of the rhizome fragments, one should sow a competitive crop, such as barley. The crop will place A. millefolium at a competitive disadvantage and further reduce its growth.

Cultural Control

In crop fields in New Zealand, a control approach has been to sow a competing crop to restrict the development of A. millefolium (Kannangara and Field, 1985a). One of the species used is Pisum sativum, which limits the seedling and plant development by reducing the light availability to the soil, and suppressing seedling development by root competition. In New Zealand, Hordeum vulgare (barley) has also been used to control the growth of A. millefollium on crop lands. H. vulgare reduces the growth rate of A. millefolium by reducing seedling and rhizome production because of low irradiance at soil level (Bourdot et al., 1985). Farhad et al. (1999) also report that the addition of nitrogen fertilizer to fields reduces the density of some weeds, A. milleifolium included, due to strong competition by the crop species.

Chemical Control

Bourdot and Butler (1985) report that rotary cultivation and the application of glyphosate greatly reduces the regrowth of A. millefolium on barley fields by up to 95%. Bourdot and Field (1988) suggest treating the seedlings with post-emergence herbicides such as bromacil and terbacil. They also report clopyralid and chlorsulfuron to be effective on seed mortality.

Studies by Sanecki et al. (2003) on the effect of four herbicides in A. millefolium showed that dicamba/2,4-D does not cause a significant reduction in the aerial biomass of the species; on the contrary, the number of flowering stems increased when compared with non-treated plants. Metsulfuron-methyl, triclopyr/picloram and glyphosate showed a significant reduction in the aerial biomass. 

Gaps in Knowledge/Research Needs

Despite the work by Ramsey et al. (2007), there is still a lack of consensus on the taxonomy of A. millefolium and the delimitation of its native range. More information and discussion on the taxonomy of this and related species are needed.

References

Acevedo-Rodríguez P; Strong MT, 2012. Catalogue of the Seed Plants of the West Indies. Smithsonian Contributions to Botany, 98:1192 pp. Washington DC, USA: Smithsonian Institution. http://botany.si.edu/Antilles/WestIndies/catalog.htm

Akram M, 2013. Minireview on Achillea millefolium Lin. Journal of Membrane Biology, 246:661-663.

Applequist WL; Moerman DE, 2011. Yarrow (Achillea millefolium L.): a neglected panacea? A review of ethnobotany, bioactivity, and biomedical research. Economic Botany, 65(2):209-225. http://www.springerlink.com/content/u62p43321815582l/

Armitage AM, 1992. Field studies of Achilles as a cut flower: longevity, spacing, and cultivar response. Journal of the American Society of HortScience, 117(1):65-67.

Baretta IP; Felizardo RA; Bimbato VF; Santos MGJdos; Kassuya CAL; Gasparotto Junior A; Silva CRda; Oliveira SMde; Ferreira J; Andreatini R, 2012. Anxiolytic-like effects of acute and chronic treatment with Achillea millefolium L. extract. Journal of Ethnopharmacology, 140(1):46-54. http://www.sciencedirect.com/science/article/pii/S0378874111008567

Barros A; Pickering CM, 2014. Non-native plant invasion in relation to tourism use of Aconcagua park, Argentina, the highest protected area in the Southern Hemisphere. Mountain Research and Development, 34(1):13-26. http://www.bioone.org/doi/full/10.1659/MRD-JOURNAL-D-13-00054.1

Beckmann M; Bruelheide H; Erfmeier A, 2011. Germination responses of three grassland species differ between native and invasive origins. Ecological Research, 26(4):763-771. http://www.springerlink.com/link.asp?id=112404

Beckmann M; Erfmeier A; Bruelheide H, 2009. A comparison of native and invasive populations of three clonal plant species in Germany and New Zealand. Journal of Biogeography, 36(5):865-878. http://www.blackwell-synergy.com/loi/jbi

Benelli G; Bedini S; Flamini G; Cosci F; Cioni PL; Amira S; Benchikh F; Laouer H; Giuseppe Gdi; Conti B, 2015. Mediterranean essential oils as effective weapons against the West Nile vector Culex pipiens and the Echinostoma intermediate host Physella acuta: what happens around? An acute toxicity survey on non-target mayflies. Parasitology Research, 114(3):1011-1021. http://link.springer.com/article/10.1007%2Fs00436-014-4267-0

Bone NJ; Thomson LJ; Ridland PM; Cole P; Hoffmann AA, 2009. Cover crops in Victorian apple orchards: effects on production, natural enemies and pests across a season. Crop Protection, 28(8):675-683. http://www.sciencedirect.com/science/journal/02612194

Bostanian NJ; Goulet H; O'Hara J; Masner L; Racette G, 2004. Toward insecticide free apple orchards: flowering plants to attract beneficial arthropods. Biocontrol Science and Technology, 14(1):25-37.

Bostock SJ, 1978. Seed germination strategies of five perennial weeds. Oecologia, 36:113-126

Bourdôt GW, 1984. Regeneration of yarrow (Achillea millefolium L.) rhizome fragments of different length from various depths in the soil. Weed Research, UK, 24(6):421-429.

Bourdôt GW; Butler JHB, 1985. Control of Achillea millefolium L. (yarrow) by rotary cultivation and glyphosate. Weed Research, UK, 25(4):251-258.

Bourdôt GW; Field RJ, 1988. Review on ecology and control of Achillea millefolium L. (yarrow) on arable land in New Zealand. New Zealand Journal of Crop and Horticultural Science, 16(2):99-108.

Bourdôt GW; Field RJ; White JGH, 1985. Growth analysis of Achillea millefolium L. (yarrow) in the presence and absence of a competitor - Hordeum vulgare L. (barley). New Phytologist, 101(3):507-519.

Bourdôt GW; Saville DJ; Field RJ, 1984. The response of Achillea millefolium L. (yarrow) to shading. New Phytologist, 97(4):653-663.

Bourdot GW; White JGH; Field RJ, 1979. Seasonality of growth and development in yarrow. In: Proceedings 32nd New Zealand Weed and Pest Control Conference, 32. 49-54.

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04/05/2016 Original text by:

Jeanine Vélez-Gavilán, University of Puerto Rico at Mayagüez

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