Tanacetum

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).

Selected References

None.

Lower Taxa

Tanacetum balsamita, Tanacetum bipinnatum, Tanacetum parthenium, Tanacetum vulgare

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