Achillea millefolium
Enable an AI agent to recognise Achillea millefolium, assess a plant or patch through its seasonal changes, and choose evidence-supported observation, cultivation, containment or sampling actions.
Research draft, second pass
A second pass drafted this model: the structure a model of this thing needs, and what is known about it in the world. The line under this one says how the second half was obtained - researched against sources, or recalled without web access, in which case nothing here was read anywhere and every claim is a lead to verify. Unreviewed either way.
Researched by: Codex + Grok
Purpose and description
Enable an AI agent to recognise Achillea millefolium, assess a plant or patch through its seasonal changes, and choose evidence-supported observation, cultivation, containment or sampling actions.
A rhizomatous perennial of Asteraceae (tribe Anthemideae), the type species of Achillea, native across temperate Eurasia and North America and distinguished by 2-3-pinnatisect fern-like leaves and a flat corymb of small white-to-pink capitula; in European pharmacognosy it is the botanical source of Millefolii herba, the whole or cut dried flowering tops.
It can be Document a provisional identification and request the missing leaf, head or specimen evidence.; Revisit marked shoots and patch boundaries to assess flowering, survival and spread.; Select and evaluate site or maintenance changes against observed plant response.; Propagate by an appropriate documented method while retaining parent or seed-source provenance.; Contain or remove unwanted growth and check for subsequent regrowth.; Collect an authorised voucher or research sample with organ, stage and source-plant traceability..
Distinguishing features
Inspect a small flowering unit with magnification: yarrow has a composite head containing ray and disc florets; a flat white cluster alone does not distinguish it from superficially similar Apiaceae such as wild carrot. Head structure is documented by [University of Texas botany](https://w3.biosci.utexas.edu/prc/K12/pages/Achillea%20millefolium.html).
Check mature leaves for repeated fine division: the Flora of North America key separates A. millefolium from A. ptarmica and A. alpina, whose leaf blades are unlobed with toothed margins. [Flora of North America key](https://www.efloras.org/florataxon.aspx?flora_id=1&taxon_id=100191).
Where the North American key applies, compare A. nobilis using multiple mature heads: it keys A. millefolium with 20-30 involucral bracts in three series and usually 5-8 ray florets, versus 10-13 bracts in one or two series and usually 8-10 rays in A. nobilis. Treat these as regional key characters requiring corroboration. [Flora of North America key](https://www.efloras.org/florataxon.aspx?flora_id=1&taxon_id=100191).
For close members of the A. millefolium complex, record leaf division, hairiness and involucral-bract margins against the chosen regional treatment; appearance alone may leave the assignment unresolved because circumscriptions differ. [Flora of North America treatment](https://www.efloras.org/florataxon.aspx?flora_id=1&taxon_id=200023010).
Scope
+ Identification from leaves, flower heads and regional botanical keys
+ Taxonomic determination, specimen evidence and cultivated or wild provenance
+ Shoot, crown and rhizome condition across seasonal stages
+ Flowering, fruiting, vegetative spread and patch persistence
+ Site relationships and observed responses to cultivation or disturbance
+ Plant-level constraints on propagation, removal and material collection
- Independent models of other Achillea species or provisionally distinguished members of the species complex
- Whole grassland, garden, soil or pollinator-community models
- Manufactured herbal products, extracts and essential-oil batches
- Clinical diagnosis, therapeutic efficacy, prescribing and dosage
- Nursery commerce, land ownership and jurisdiction-wide conservation rules
Characteristics
- Taxonomic determination
- Registry entry, applied botanical treatment, determiner, date and supporting specimen or images Makes an identification reproducible without silently equating different species circumscriptions.
- Identification confidence
- Provisional; supported by regional key; specialist verified; conflicting evidence Controls whether observation, propagation or material collection can proceed.
- Leaf dissection
- Division order, ultimate-segment shape and leaf position; unknown when obscured Supports separation from other yarrows and documents variation within the complex.
- Flower-head characters
- Head and ray dimensions in mm; ray and involucral-bract counts per head; bract-series count Provides inspectable evidence beyond overall flower-cluster appearance.
- Seasonal stage
- Vegetative; budding; flowering; fruiting; senescent; dormant suspected; dead confirmed; mixed Determines which identification evidence and interventions are available.
- Patch extent
- Occupied area in m², cover in %, mapped boundary and observation date Tracks establishment or encroachment without assuming every shoot is a separate individual.
- Below-ground continuity
- Observed rhizome connection between shoots; suspected connection; unexamined Supports decisions about division, sampling and removal while preserving uncertainty about clone boundaries.
- Crown and shoot condition
- Living growth, dieback, lodging, discoloration, lesions and visible feeding damage, with affected extent Distinguishes observed injury from an unverified diagnosis.
- Establishment provenance
- Spontaneous; sown; planted division; nursery plant; unknown, with source locality or cultivar claim Supports restoration suitability and prevents local origin being inferred from the species name.
- Site exposure and drainage
- Sun exposure; freely drained, intermittently saturated or persistently saturated substrate; observation method Helps interpret plant condition and select cultivation changes.
- Collection suitability
- Unassessed; eligible for a specified purpose; restricted; unsuitable, with evidence Separates botanical identity from permission, contamination status and suitability for a particular downstream use.
Where this came from
wikidata · CC0 1.0
Drafted structure
Bundle to layer to finding to question, as the second pass will find it: 6 bundles · 11 layers · 18 findings · 36 questions.
Identity and circumscription Establish what evidence warrants assigning a plant to the registered Achillea millefolium concept.
The species name is insufficient when regional treatments and cultivated material introduce ambiguity.
Vegetative and floral diagnosis
Combine mature leaf and individual flower-head evidence.
Diagnostic character agreement
Record which characters agree with the applicable key, which conflict and which cannot yet be observed.
- Do mature leaves and dissected flower heads jointly satisfy the regional key for A. millefolium? definition
- Which head dimensions, floret counts and bract characters were measured, and on how many heads? measurement
- Which competing identification remains plausible, and what additional observation would discriminate it? boundary
Taxonomic and cultivated provenance
Preserve the meaning and origin of a determination.
Name application evidence
Connect the registry assignment to a dated treatment and evidence; retain cultivar or hybrid claims without treating a supplier label as verification.
- Which flora or taxonomic authority defines A. millefolium for this determination? provenance
- What voucher, photographs, determiner or nursery records support the identification and origin? provenance
- Does the evidence support this entry, only the broader species complex, or an unresolved cultivated Achillea? boundary
Seasonal body and persistence Track the living perennial through shoot turnover and below-ground persistence.
Loss of visible flowering stems does not by itself establish loss of the plant.
Shoot and flowering cycle
Represent vegetative growth, flowering, fruiting and seasonal decline at the observation site.
Stage-resolved condition
Record mixed stages within a patch and distinguish dated observations from assumed flowering calendars.
- What proportions of observed shoots are vegetative, budding, flowering, fruiting or senescent? measurement
- Did a change in flowering follow season, mowing, grazing or another recorded event? provenance
Crown, rhizome and shoot continuity
Connect visible shoots to persistent growth structures where evidence permits.
Persistence unit
Distinguish a shoot, a sampled connected division and a mapped patch; leave genetic individuality unresolved without appropriate evidence.
- Is the tracked unit one shoot, an observed connected crown-and-rhizome unit or a patch of uncertain connectivity? definition
- What living buds, roots or renewed shoots support persistence after above-ground dieback? measurement
- Can continuity be established by revisiting marked growth, or is an authorised below-ground inspection necessary? action
Site fit and plant condition Relate yarrow condition to exposure, drainage and disturbance.
Cultivation decisions require evidence about the occupied site and the plant's response there.
Exposure and rooting environment
Use site observations to assess growing conditions; RHS guidance describes Achillea as favouring sun and well-drained soil. [RHS growing context](https://www.rhs.org.uk/plants/achillea).
Site-condition match
Record exposure and drainage alongside establishment, flowering and stem stability rather than assigning universal thresholds.
- What sun exposure and duration of soil saturation occur where this yarrow is rooted? measurement
- Which observed condition supports changing irrigation, drainage, shading or planting position? action
Injury and recovery
Assess damage and recovery without confusing symptoms, seasonal change and diagnosis.
Damage pattern and response
Locate damage on leaves, flowering stems and crowns, and connect recovery observations to dated disturbances.
- Which organs show lesions, discoloration, feeding damage, collapse or dieback, and how extensive is each symptom? measurement
- What evidence distinguishes seasonal senescence or cutting damage from a suspected pest, pathogen or rooting problem? boundary
- What follow-up observation would establish recovery or justify specialist diagnosis? action
Reproduction and patch management Track flowering, recruitment and vegetative expansion in relation to the intended role of the patch.
A useful retained patch and unwanted encroachment require different decisions about the same growth.
Flowering and recruitment
Separate flower production, insect visits, fruit formation and demonstrated seedling establishment.
Reproductive outcome
Record reproductive evidence without treating an insect visit as proven pollination or a new shoot as a seedling.
- What flowering heads, developing fruits and independently identified seedlings were observed? measurement
- Does the evidence establish insect visitation, successful fruit formation or viable seed production? boundary
- Should flower heads be retained or removed given the documented goal for this patch? action
Vegetative expansion and control
Track patch boundaries and post-intervention regrowth.
Spread and intervention outcome
Compare mapped extent before and after division, cutting or removal, retaining uncertainty about the origin of new shoots.
- How far has the occupied boundary moved between dated surveys? measurement
- Is new growth connected to existing rhizomes, independently established or of unresolved origin? boundary
- What propagation, containment or removal action fits the site objective, and when will regrowth be checked? action
Collection and use boundaries Govern the transition from living yarrow to collected specimens or material.
Botanical identity alone does not establish permission to collect or suitability for human use.
Sample identity and origin
Preserve the connection between collected organs and the determined source plant.
Traceable yarrow sample
Identify the sampled organs, seasonal stage, collection location and collection authority; record potential contamination as evidence or uncertainty.
- Which determined plant or patch supplied the leaves, flowering tops, fruits or below-ground material? provenance
- What permission and patch-condition evidence support collecting the proposed amount? action
- What site history or testing bears on pesticide exposure, contamination or mixing with other plants? provenance
Human-use handoff
Keep plant identification separate from product and clinical decisions; EMA reports hypersensitivity reactions and restrictions for yarrow herb medicines. [EMA yarrow herb assessment](https://www.ema.europa.eu/en/medicines/herbal/millefolii-herba).
Purpose-specific use gate
Record the intended destination and relevant unresolved constraints, then hand processing, formulation and therapeutic decisions to their owning models.
- Is the material intended for a voucher, cultivation, laboratory analysis, food or a medicinal product? definition
- Which downstream assessment must establish suitability for that purpose, including relevant allergy constraints? boundary
- What missing identity, quality or use-specific evidence requires withholding a recommendation to consume or apply the material? action
Evidence and external alignment What the world already says about this thing, gathered so the model can be checked against it.
A model that cannot be lined up against existing standards, identifiers and practice cannot be adopted by anyone who already uses them.
Reported evidence
Findings from the breadth pass, kept separate from the structural claims.
Kinds and varieties
Reported by the breadth pass; each item needs checking against its source before it becomes normative.
- European common yarrow (A. millefolium subsp. millefolium): the Old World, usually hexaploid plants that underwrite the pharmacopoeial concept
- Native North American yarrow (often treated as A. lanulosa, subsp. lanulosa or var. occidentalis): typically tetraploid plants with narrower leaf segments held in more than one plane
- Boreal and Arctic yarrow (var. borealis / A. borealis)
- Pacific and California races (var. californica, var. pacifica, and the California endemic var. puberula)
- Millefolii herba: dried flowering tops as a crude herbal drug
- Millefolii flos: yarrow flower, a separately monographed herbal substance
- Ornamental cultivars selected for ray colour and habit (for example 'Paprika', 'Cerise Queen', RHS Award of Garden Merit clones)
- Essential-oil chemotypes: proazulene/chamazulene-rich (blue oil) versus non-azulene (colourless to yellow oil)
- Which of these kinds and varieties hold for the sense of Achillea millefolium this model covers, and on what evidence? provenance
Identifiers and schemes
Reported by the breadth pass; each item needs checking against its source before it becomes normative.
- Wikidata - Q25444 - Item for the species Achillea millefolium
- Linnaean binomial / protologue - Achillea millefolium L., Sp. Pl. 2: 899. 1753 - Original publication cited by Flora of North America
- European Pharmacopoeia monograph - Yarrow - Millefolii herba (07/2014:1382) - EDQM crude-drug monograph for dried flowering tops
- EMA herbal substance name - Millefolii herba; Achillea millefolium L., herba - Latin and botanical names used in HMPC documents EMA/HMPC/376416/2019
- CAS Registry Number - 977000-16-0 - PubChem listing for Achillea millefolium as a substance, not a discrete molecule
- MeSH - Achillea millefolium - NLM Medical Subject Headings entry term
- French Pharmacopoeia (homoeopathic) - Achillea millefolium ad praeparationes homoeopathicas / Millefolium for homoeopathic preparations - Fresh whole flowering plant as starting material
- Which of these identifiers and schemes hold for the sense of Achillea millefolium this model covers, and on what evidence? provenance
Standards and regulation
Reported by the breadth pass; each item needs checking against its source before it becomes normative.
- European Pharmacopoeia monograph Yarrow - Millefolii herba (07/2014:1382), issued by EDQM: dried flowering tops must contain at least 2 ml/kg essential oil and at least 0.02% proazulenes calculated as chamazulene
- European Union herbal monograph on Achillea millefolium L., herba (EMA/HMPC/376416/2019), Committee on Herbal Medicinal Products: traditional-use registration under Directive 2001/83/EC Article 16a
- Commission Decision 2008/911/EC as amended by Implementing Decision (EU) 2022/1316: Union list entry for Achillea millefolium L., herba (Yarrow) with specified aqueous preparations
- Directive 2001/83/EC of the European Parliament and of the Council: framework for herbal medicinal products and traditional herbal medicinal products
- EMA public statement on herbal medicinal products containing thujone (EMA/HMPC/732886/2010): relevant because yarrow oil contains small amounts of thujone
- French Pharmacopoeia 2007: Yarrow for homoeopathic preparations (fresh flowering plant; foreign matter max. 5%; loss on drying min. 55.0%)
- United States: yarrow flower was formerly official in the USP; FDA has permitted yarrow in alcoholic beverages, but it is not a current USP-NF botanical monograph on the evidence read here
- Which of these standards and regulation hold for the sense of Achillea millefolium this model covers, and on what evidence? provenance
Real-world use
Reported by the breadth pass; each item needs checking against its source before it becomes normative.
- Traditional herbal medicinal product in the EU: comminuted herb as tea, or aqueous dry extracts, for temporary loss of appetite and mild spasmodic gastrointestinal complaints including bloating and flatulence
- Same herbal preparations used for minor menstrual abdominal cramps and, externally, for small superficial wounds of skin and mucosa
- Fresh or dried herb in folk and Native American practice as a wound styptic, fever diaphoretic, toothache chew, and eyewash; crushed leaves historically used to staunch nosebleeds
- Ornamental and pollinator plant in drought-tolerant, meadow and butterfly gardens; also used as a companion plant and for erosion control on dry soils
- Young leaves eaten sparingly in salad or as a bitter tea; flowers and herb used in some bitters and liquors, and historically as a gruit-type beer flavouring
- Dried stalks of subsp. millefolium used in Chinese I Ching (yarrow-stalk) divination
- Introduced into New Zealand and Australian pastures as a deep-rooted, mineral-rich forage component; now also a roadside and grassland weed there
- Wool dye (green to yellow depending on mordant) and source of a dark-blue essential oil when proazulenes are present
- Which of these real-world use hold for the sense of Achillea millefolium this model covers, and on what evidence? provenance
Typical measurements
Reported by the breadth pass; each item needs checking against its source before it becomes normative.
- Shoot height - 0.2-1 (Flora of North America often 0.06-0.65+) - m
- Leaf blade length × width - 3.5-35+ × 0.5-3.5 (common field leaves often 5-20 cm long) - cm
- Ray-floret lamina - 1.5-3 × 1.5-3 - mm
- Cypsela length - 1-2 - mm
- Essential oil in dried flowering tops (Ph. Eur. minimum) - ≥ 2 (reported range about 0.2-5.9% of drug) - ml/kg
- Proazulenes as chamazulene (Ph. Eur. minimum, dried drug) - ≥ 0.02 - % m/m
- Herbal-tea daily dose in the EU monograph assessment - up to 16 (as herbal substance) - g/day
- Elevational range - 0-3500 - m
- Which of these typical measurements hold for the sense of Achillea millefolium this model covers, and on what evidence? provenance
Failure modes and hazards
Reported by the breadth pass; each item needs checking against its source before it becomes normative.
- Allergic contact dermatitis from sesquiterpene lactones; people sensitised to other Asteraceae often cross-react
- ASPCA: toxic to dogs, cats and horses (vomiting, diarrhoea, increased urination, dermatitis)
- Taints the flavour of cows' milk if grazed
- Rhizomatous spread makes it weedy in lawns, gardens and some pastures and hard to eradicate once established
- Root rot in poorly drained soils; occasional powdery mildew and stem rot
- Chemotype mismatch: hexaploid European subsp. millefolium oil is often non-azulenic, so a 'yarrow oil' may lack the chamazulene the blue-oil trade expects
- Small thujone content; high-dose or long-term extracts have shown toxicity in animal work even though ordinary tea doses are treated as traditional-use safe in adults and adolescents over 12
- Not for use in known Compositae hypersensitivity; HMPC: medical advice if GI symptoms persist beyond two weeks or wound/menstrual use beyond one week
- Which of these failure modes and hazards hold for the sense of Achillea millefolium this model covers, and on what evidence? provenance
Regional variation
Reported by the breadth pass; each item needs checking against its source before it becomes normative.
- Taxonomic practice: European floras and the pharmacopoeia treat a relatively narrow A. millefolium; Flora of North America lumps native and introduced races as one variable species, while some North-eastern treatments still separate native lanulosa/borealis from garden-introduced subsp. millefolium
- English folk names (milfoil, soldier's woundwort, nosebleed plant, devil's nettle) versus French achillée millefeuille / herbe-à-dinde, German Schafgarbe, Norwegian ryllik, Unani brinjasif, Chinese yarrow-stalk use rather than the European wound-herb emphasis
- Australia and New Zealand: a deliberately introduced pasture plant that is now also classed as an environmental and garden weed
- California: several named coastal and endemic varieties; absent from the Colorado and Mojave Deserts
- Pharmaceutical versus horticultural trade: crude-drug 'yarrow' means white-to-pink wild-type flowering tops; garden centres sell coloured-ray cultivars that are not the Ph. Eur. article
- Which of these regional variation hold for the sense of Achillea millefolium this model covers, and on what evidence? provenance
Neighbouring kinds and how to tell them apart
Reported by the breadth pass; each item needs checking against its source before it becomes normative.
- Tanacetum vulgare (tansy) - Tansy has button-like yellow discoid heads without obvious rays and a strong camphor scent; yarrow has a flat corymb of small radiate heads (white to pink) and 2-3-pinnatisect leaves
- Achillea filipendulina (fernleaf yarrow) - Golden-yellow dense corymbs and leaves divided into relatively broad toothed segments with dense appressed hairs; A. millefolium has very narrow segments and usually white, pink or mauve rays
- Achillea distans subsp. tanacetifolia (tansyleaf milfoil) - Rachis wings 1-2 mm wide and usually toothed or lobed between the pinnae; A. millefolium is dissected almost to the midrib into very narrow segments
- Achillea ligustica - Mid-stem leaves usually with 10 or fewer lobes held in one plane and an ovate outline; A. millefolium mid-stem leaves have 15 or more primary divisions not in one plane and a lanceolate to linear outline
- Daucus carota (wild carrot / Queen Anne's lace) - An umbel of five-petalled flowers, often with a single dark central floret, versus yarrow's compound of many tiny radiate capitula; carrot foliage is 2-3-pinnate but not in a corymb of daisy heads
- Matricaria chamomilla / Chamaemelum nobile (chamomiles) - Solitary (or loosely branched) larger daisy heads with hollow receptacles in German chamomile; yarrow packs many much smaller heads into a dense flat corymb on a single plant
- Which of these neighbouring kinds and how to tell them apart hold for the sense of Achillea millefolium this model covers, and on what evidence? provenance
Sources
- Achillea millefolium - Morphology, height and leaf ranges, subspecies and North American varieties, native range, cultivation, traditional and food uses, I Ching stalks, dermatitis and veterinary toxicity
- Achillea millefolium - Flora of North America treatment: protologue (Sp. Pl. 2: 899. 1753), measurements of stems, leaves, heads and cypselae, and the one-species-versus-many-names problem in North America
- Millefolii herba - herbal medicinal product - HMPC traditional-use indications (appetite, mild GI spasm, menstrual cramps, small superficial wounds), age restriction, and the herbal name Millefolii herba
- Assessment report on Achillea millefolium L., herba (Revision 1), EMA/HMPC/376415/2019 - Ph. Eur. quality limits for essential oil and proazulenes, maximum daily herbal-tea dose, thujone caution, and national pharmacopoeial history
- Commission Implementing Decision (EU) 2022/1316 amending Decision 2008/911/EC (Union list entry on Achillea millefolium L., herba) - Legal listing of Yarrow / Millefolii herba, Ph. Eur. monograph 07/2014:1382, allowed preparations and traditional indications
- Millefolii Herba (Yarrow) - Drug definition (dried flowering tops), essential-oil range and marker constituents, internal and external therapeutic indications
- Medicinal plant of the year 2025 - German pharmacognosy practice: Millefolii herba as flowering shoot tips, EuAB monograph, HMPC traditional-use framing
- Achillea millefolium - common yarrow - New England practice of distinguishing introduced subsp. millefolium from native lanulosa/borealis material, and the leaf-plane test versus A. ligustica
- Dog Daisy - Achillea millefolium - Garden and landscape use, contact dermatitis, pet hazard, weedy rhizomatous spread, and confusion with Tanacetum vulgare
- Achillea millefolium L. - Australian weed status and the leaf-rachis tests that separate A. millefolium from A. distans subsp. tanacetifolia and A. filipendulina
- Achillea millefolium - CAS 977000-16-0, MeSH term, and GHS statements applied to yarrow-derived materials (skin irritation and sensitisation)
- Yarrow for homoeopathic preparations / Millefolium for homoeopathic preparations - French Pharmacopoeia definition of the fresh flowering plant, macroscopic characters, and loss-on-drying test
- Yarrow (Achillea millefolium L.): A Neglected Panacea? A Review of Ethnobotany, Bioactivity, and Biomedical Research - Worldwide ethnobotanical uses and the unresolved A. millefolium species-complex taxonomy (narrow European circumscription versus broad Holarctic species)
What the second pass must settle
- Which taxonomic authority and geographic treatment should define the registry entry's boundary within the A. millefolium complex?
- Which regional diagnostic character combinations reliably separate the relevant close species, and how should differing published bract counts be reconciled?
- What evidence is sufficient to establish local wild provenance or cultivar identity for restoration and propagation decisions?
- Which locally measured seasonal patterns and recovery responses should guide mowing, division, containment and mortality assessment?
- Which purpose-specific sampling, contamination and composition assessments are required before collected material can be accepted by a downstream food, research or medicinal-product model?