This section is from the book "An Illustrated Flora Of The Northern United States, Canada And The British Possessions Vol3", by Nathaniel Lord Britton, Addison Brown. Also available from Amazon: An Illustrated Flora of the Northern United States, Canada and the British Possessions. 3 Volume Set..
Erect, strongly aromatic herbs, our species perennials, with alternate, 1-3-pinnately dissected or divided leaves, and numerous small corymbose heads of tubular flowers, or with rays sometimes present and imperfectly developed. Involucre hemispheric, depressed, or campanulate, its bracts appressed, imbricated in several series. Receptacle flat or convex, naked. Marginal flowers pistillate, fertile, their corollas 2-5-toothed or lobed, sometimes produced into short rays. Disk-flowers perfect, fertile, their corollas 5-toothed. Anthers obtuse and entire at the base, their tips broad. Style-branches truncate and penicillate at the summit. Achenes 5-angled or 5-ribbed, truncate or obtuse. Pappus none, or a short crown. [From tanasie, old French for tansy; Greek, athanasia, immortality.!
About 30 species, natives of the northern hemisphere. Besides the following, another occurs in California. Type species: Tanacettim vulgare L.
Glabrous, or nearly so; heads numerous, 3"-5" broad.
1. T. vulgare.
Villous-pubescent; heads few, 6"-8" broad.
2. T. huronense.
Tanacetum vulgare L. Sp. Pl. 844. 1753. Tanacetum vulgare crispum DC. Prodr. 6: 128.
Stem stout, usually simple up to the inflorescence, glabrous, or sparingly pubescent, 1 1/2°-3° high. Leaves pinnately divided into linear-oblong, pinnatifid or incised, often crisped segments, the lobes acute, usually serrate; lower segments of the leaves often smaller than the others; basal leaves often 1° long; heads commonly numerous, 3"-5" broad, rather short-peduncled; involucre depressed-hemispheric, its bracts oblong-lanceolate, obtuse, or the outer acute, slightly pubescent or ciliate; receptacle flat; flowers yellow; marginal corollas with short oblique 3-toothed limbs; pappus a short crown.
Along roadsides, mostly escaped from gardens, Nova Scotia and Ontario to Minnesota, Oregon, Nevada, North Carolina and Missouri. Naturalized or adventive from Europe. Bitter-buttons. Hindheal. Ginger-plant. July-Sept.
Tanacetum huronense Nutt. Gen. 2: 141. 1818.
Villous-pubescent throughout, at least when young, less so when mature, 1°-2° high. Leaves 2-pinnately divided, the lobes dentate or incised, acute, the lower segments commonly smaller than the others; heads 1- 8, 6"- 8" broad, on very stout pubescent peduncles; involucre depressed-hemispheric; marginal flowers with 3-5-lobed limbs, often expanded into short rays; pappus a short crown.
In moist soil, especially along streams or lakes, New Brunswick to Hudson Bay, Maine, Lake Superior, Alaska and Oregon. July-Sept.