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..
Liatris pycnostachya Michx. Fl. Bor. Am. 2: 91. 1803. Lacinaria pycnostachya Kuntze, Rev. Gen. Pl. 349. 1891.
Hirsute-pubescent above, usually glabrous below, 2°-5° high, very leafy. Lower leaves linear-lanceolate, narrowed below the middle into a slender margined petiole, acuminate at the apex, often 1° long and V wide, the upper much smaller, linear-subulate, rigid, punctate; spikes very dense, 6'-18' long; heads 4"-6" long, 3-6-flowered; involucre oblong or cylindric, its bracts oblong, pubescent and ciliate with acute, spreading, colored tips; flowers purple; pappus barbellate or roughened, scarcely plumose.
Finely pubescent, at least above, 1°-6° high. Lower leaves oblanceolate, spatulate or oblong-lanceolate, narrowed into a margined petiole, acute or obtusish at the apex, often 1° long and 1 1/2' wide; upper leaves linear or linear-lanceolate, acute, or sometimes very obtuse, much smaller, all densely punctate; heads hemispheric, 1/2'-1' broad, 15-45-flowered, on stout peduncles 2"-2' long, or sometimes sessile; bracts of the involucre imbricated in 5 or 6 series, spatulate-linear, oblanceolate or obovate, rounded at the apex, appressed, their tips dry and scarious, often colored; flowers bluish purple; pappus barbellate.
In dry soil, Maine to Florida, western Ontario, Manitoba, Nebraska and Texas. Consists of many races, differing in leaf-form and size of heads. Called also blue blazing-star, gray feather, rattlesnake-master, devil's-bite. Aug.-Sept.
Serrulata spicata L. Sp. Pl. 819. 1753. Liatris spicata Willd. Sp. Pl. 3: 1636. 1804. ?Liatris pumila Lodd. Bot. Cab. pl. 147. 1821. L. spicata Kuntze, Rev. Gen. Pl. 349. 1891.
Glabrous or nearly so, 2°-6° high. Lower leaves linear-lanceolate or linear-oblong, usually blunt-pointed, sometimes 1° long and 5" wide, the upper linear or even subulate, somewhat or obscurely punctate; spike generally dense, 4'-15' long; heads -short-oblong or cylindric, 5-13-flowered, 2 "-4" broad, mostly sessile; involucre subcam-panulate, rounded or obtuse at the base, its bracts appressed, oblong, obtuse . and scarious-margined at the apex, obscurely punctate, imbricated in 4-6 series; flowers blue-purple, occasionally white; pappus roughened or barbellate.
Lacinaria kansana Britton, of Kansas, differs in having a short, very dense spike, a more leafy stem, the involucral bracts purple and the pappus plumose.