8. Artemisia ludoviciana Nutt. (white sage, western mugwort)

Pl. 226 f, g; Map 948

Plants perennial herbs, with rhizomes, strongly aromatic when bruised. Stems 30–100 cm long, erect or ascending from sometimes spreading bases, densely pubescent with woolly or felty hairs, at least toward the tip, also minutely glandular. Leaves 1–11 cm long, short-petiolate to sessile, lacking stipulelike lobes or teeth at the base. Leaf blades unlobed and/or with 1–4 pairs of lobes, linear or lanceolate to oblong-elliptic in outline, the lobes linear to oblong-linear or narrowly oblong-triangular in outline, entire or rarely with a pair of deep lobes, the margins not toothed, the ultimate segments or lobes 1–9 mm wide (mostly more than 2 mm wide), the margins flat or curled under, sharply pointed at the tip, both surfaces densely pubescent with woolly to felty hairs or the upper surface sparsely hairy to glabrous, also minutely glandular. Inflorescences appearing as open, leafy panicles, the branches spicate with usually relatively loosely spaced, sessile to short-stalked heads. Heads with the central florets perfect and the marginal florets pistillate or less commonly perfect, thus all of the florets potentially producing fruits. Involucre 2.5–5.0 mm long, the bracts in 3 or 4 overlapping rows, the often indistinct main body linear to oblong-elliptic, densely woolly-hairy and minutely glandular, the innermost with relatively narrow to broad, thin, transparent margins and tip, these glabrous. Receptacle naked. Corollas 1.5–2.8 mm long. Fruits 0.8–1.2 mm long, narrowly oblong-obovoid, faintly lined, tan to yellowish brown, shiny. 2n=18, 36, 72. June–October.

Scattered in the western and northern halves of the state, uncommon farther south and east (western U.S. east to Illinois and Louisiana; Canada, Mexico, Central America; introduced farther eastward in the U.S.). Glades, ledges and tops of bluffs, openings of mesic to dry upland forest, bottomland and upland prairies, sand prairies, loess hill prairies, banks of rivers, and rarely marshes; also pastures, old fields, fencerows, cemeteries, railroads, roadsides, and open, disturbed areas.

This widespread species was described by one of the first two professional botanists to visit Missouri, Thomas Nuttall, based on plants that he collected along the banks of the Mississippi River near St. Louis during the winter of 1810–1811. Morphological variation across the distributional range is quite complex (Keck, 1946). Most authors have accepted some sort of infraspecific classification, as there appear to be geographic and/or habitat differences between some of the entities, especially in the western United States. However, the characters emphasized to separate taxa have not been applied uniformly by different authors. In Missouri, the two types of plants present appear to sort out reasonably well, although a number of specimens appear intermediate.