Nabalus asper (Michx.) Torr. & A. Gray

Rough White Lettuce

© SRTurner

Family - Asteraceae/Cichorieae

Habit - Perennial forb with tuberous-thickened rootstocks and milky sap.

Stems - Ascending to erect, to 1.7 m, slender to stout, moderately to densely pubescent with short, spreading hairs and minute, curled hairs above the midpoint, often glabrous or nearly so toward the base, often purplish-tinged or with dark purple mottling, not glaucous.

	Stem and leaves.
© SRTurner

Leaves - Basal and alternate, sessile to short-petiolate. Basal and lowermost stem leaves with the blades 4-11 cm long, more or less obovate, the margins entire or with few to several often irregular, fine teeth or rarely shallow lobes. Lower, median, and upper leaves gradually reduced, sessile, the blade entire or more commonly finely toothed, rarely more deeply toothed or shallowly pinnately lobed, narrowly lanceolate to lanceolate, oblong-elliptic, or rarely ovate. Leaf surfaces minutely roughened, the undersurface also with short, stiff, stout hairs and often also inconspicuously pubescent with short, curled hairs along at least the main veins.

	Leaf.
© SRTurner

	Leaf abaxial surface.
© SRTurner

Inflorescences - Appearing spicate, as narrowly cylindrical panicles, or as small, dense terminal or axillary clusters of heads along an unbranched main stem, the heads mostly ascending.

	Inflorescence.
© SRTurner

Heads - Ligulate. Involucres cylindrical, 12-17 mm long, the 8-10 inner bracts narrowly rounded to more commonly sharply pointed at the tip, the surface pubescent with relatively coarse, stiff, spreading to ascending hairs, the margins frequently pubescent with minute, curled hairs toward the tip, yellowish green to pale green, often with a darker green to dark purplish-tinged base and/or tip, not glaucous or pebbled. Receptacle naked.

	Flowering heads.
© SRTurner

	Flowering heads.
© SRTurner

	Involucres.
© SRTurner

Flowers - Ligulate florets 11-14, the corollas 9-17 mm long, cream-colored to pale yellow. Pappus 6-8 mm long, usually straw-colored.

	Ligulate florets.
© SRTurner

Fruit - Achenes 5-6 mm long, yellowish brown.

Flowering - August - October.

Habitat - Prairies, glades, upland forest openings, savannas, railroads, roadsides.

Origin - Native to North America.

Lookalikes - Nabalus crepidineus.

Other info. - This striking species is scattered across most of Missouri, though it is not often encountered. Its main range comprises a cluster of a dozen or so states within the U.S. Midwest, centered roughly on Missouri and Iowa. It is recognized by its rough and hairy stems and leaves, and pale ligulate flowering heads. Relative to other members of the genus, its inflorescences tend to be narrower and can appear almost spikelike. It also occupies much drier habitats than N. crepidineus.

A former name for this species was Prenanthes aspera Michx.

Photographs taken at Shaw Nature Reserve, Franklin County, MO, 9-8-2012, Tucker Prairie, Callaway County, MO, 8-21-2015, and Victoria Glade, Jefferson County, MO, 9-19-2016 (SRTurner).