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..
Artemisia pontica L. Sp. Pl. 847. 1753.
Perennial; stem branched, glabrous or canescent, 1°-3° high. Leaves 1 1/2'-2.1/2' long, 2-3-pinnately dissected into short narrow lobes less than 1" wide, canescent on both sides, or tomentose beneath, the lower petioled and the petioles somewhat clasping or auricled at the base, the upper mostly linear and entire; heads numerous, 1"-2" broad, drooping, slender-peduncled; involucre hemispheric, canescent, its bracts oblong or obovate, obtuse, the outer short, lanceolate; receptacle glabrous; central flowers fertile.
Waste grounds, Massachusetts, New Jersey, Pennsylvania, Ohio and Colorado. Fugitive or adventive from central Europe. July-Aug.
Densely white-woolly all over; stem erect, much branched, the branches strict, bearing very numerous small heads forming a narrow dense panicle. Leaves numerous, crowded, the lower pinnately divided into 3-7 narrowly linear revolute-margined segments i" wide or less, greenish above; upper leaves mostly narrowly linear and entire; heads oblong-oval, sessile, or very short-peduncled, erect, or somewhat spreading, 1 1/2" long; involucre very woolly, its bracts ovate-lanceolate to oblong-lanceolate, acute; receptacle naked.
Plains, Kansas to Colorado and New Mexico. Introduced in Missouri. July-Sent.
Artemisia serra'a Nutt. Gen. 2: 142. 1818.
Perennial; stem stout, tomentose or becoming glabrous, much branched, 5°-10° high. Leaves lanceolate, 2'-6' long, 3"-12" wide, densely white-tomentose beneath, dark green and glabrous above, acuminate at the apex, narrowed to a sessile base, or the lowest petioled, sharply serrate or incised, or the upper entire; heads very numerous, greenish, erect, about 1 1/2" broad, sessile or short-peduncled in panicled spikes or racemes; involucre canescent, its bracts oblong, or the outer ones lanceolate; receptacle naked; central flowers fertile.
Prairies, Illinois to Minnesota and Dakota. Introduced on the Mohawk River, near Schenectady, N. Y. Aug.-Oct.
Artemisia longifolia Nutt. Gen. 2: 142. 1818.
Perennial; stem densely white-tomentose, branched, 2°-5° high. Leaves linear or linear-lanceolate, elongated, entire, 2'-5' long, 1"-5" wide, acuminate, tapering to a sessile base, or the lower petioled, densely white-tomentose on both sides, or becoming green and glabrate above; heads numerous, erect, spicate-paniculate, about 2" broad; involucre tomentose, its bracts narrowly oblong; receptacle naked; central flowers fertile.
In dry rocky soil, western Nebraska to Minnesota, Idaho, Oregon and Saskatchewan. Aug.-Sept.