Artemisia longifolia

Artemisia longifolia, commonly known as the longleaf wormwood or longleaf mugwort, is a species of flowering plant in the Asteraceae family. It is found in Canada and the midwest United States.

Description
It is a perennial herb growing from 20–80 cm tall. It usually has anywhere from 3–20 erect, gray-green stems, but has sometimes reached over 21. The leaves are white on the lower side with densely matted, white, woolly hairs and green on the upper surface with few to almost no hairs, 3–12 cm × <1 cm, linear to linear-lanceolate and are entire with smooth, down-rolled edges or rarely with a few slender teeth. The tiny, discoid florets form yellow to brownish, woolly,4-5 mm high, erect flowerheads, which form narrow, branched raceme-like or panicle-like clusters from mid-summer to early fall (July-September). The fruits are tiny, seed-like achenes, that do not have a pappus.

Discovery
It was discovered by Meriwether Lewis and William Clark on October 1, 1804 during their expedition.