Tanacetum

Linnaeus

Sp. Pl. 2: 843. 1753

,

Gen. Pl. ed. 5, 366. 1754

Common names: Tansy tanaisie
Etymology: Derivation unknown possibly Greek athanasia, immortality, through Medieval Latin tanazita
Treatment appears in FNA Volume 19. Treatment on page 489. Mentioned on page 31, 48, 49, 52, 53, 68, 486, 488.
Perennials [annuals, subshrubs], 5–150 cm (usually rhizomatous; usually aromatic). Stems 1 or 2–5+, erect or prostrate to ascending, branched proximally and/or distally, glabrous or hairy (hairs basifixed and/or medifixed, sometimes stellate). Leaves basal and/or cauline; alternate; petiolate or sessile; blades mostly obovate to spatulate, usually 1–3-pinnately lobed, ultimate margins entire, crenate, or dentate, faces glabrous or hairy. Heads usually radiate, sometimes disciform (or quasi-radiate or -radiant), usually in lax to dense, corymbiform arrays, rarely borne singly. Involucres mostly hemispheric or broader, (3–)5–22+ mm diam. Phyllaries persistent, (20–)30–60+ in (2–)3–5+ series, distinct, ± ovate to oblong or oblong to lanceolate or lance-linear (sometimes carinate), unequal, margins and apices (pale to dark brown or blackish) scarious (tips sometimes dilated). Receptacles flat to conic or hemispheric (sometimes hairy), epaleate. Ray florets usually 10–21+ (pistillate and fertile or neuter; corollas pale yellow to yellow or white, usually with yellowish bases [pink], laminae oblong to flabellate), sometimes 0 (in disciform or quasi-radiate or -radiant heads, peripheral pistillate florets 8–30+; corollas pale yellow, ± zygomorphic, lobes 3–4, sometimes ± raylike). Disc florets 60–300+, bisexual, fertile; corollas yellow, tubes ± cylindric, throats narrowly funnelform to campanulate, lobes (4–)5, ± deltate. Cypselae obconic or ± columnar (circular in cross section), ribs (4–)5–10(–12+), faces usually gland-dotted, sometimes glabrous (pericarps without myxogenic cells or resin sacs, embryo sac development tetrasporic); pappi usually coroniform, rarely 0 [distinct scales or each pappus an adaxial auricle]. x = 9 (polyploidy).

Distribution

North America, Europe, Asia, n Africa, some species widely cultivated.

Discussion

Species 160 (4 in the flora).

References

None.

Key

1 Leaves usually not pinnately lobed (sometimes with 1–4+ lateral lobes near bases of blades), ultimate margins ± crenate Tanacetum balsamita
1 Leaves usually 1–3-pinnately lobed, ultimate margins entire or dentate > 2
2 Leaf blades 1–2-pinnately lobed (primary lobes 3–5 pairs, ± ovate), faces (at least abaxial) usually puberulent; ray florets 10–21+ (more in "doubles"), corollas white, laminae 2–8(–12+) mm; pappi 0 or coroniform (0.1–0.2+ mm) Tanacetum parthenium
2 Leaf blades 2–3-pinnately lobed (primary lobes 4–24+ pairs, ± oblong to elliptic or linear), faces usually arachno-villous to villous, sometimes glabrescent or glabrous; ray florets 0 or 8–30+, corollas pale yellow to yellow, laminae 1–8+ mm; pappi coroniform (0.1–0.5+ mm) > 3
3 Leaves: faces glabrous or sparsely hairy; heads (disciform) 20–200 in corymbiform arrays; involucres 5–10 mm diam Tanacetum vulgare
3 Leaves: faces usually ± villous or arachno-villous to lanate, sometimes glabrescent or glabrate; heads (radiate, quasi-radiant or -radiate, or disciform) (2–)5–12(–20+) in corymbiform arrays or borne singly; involucres 8–22+ mm diam Tanacetum bipinnatum