Biennials or short-lived perennials, 30-60 cm; taprooted. Stems densely and persistently white-tomentose, usually with stipitate-glandular hairs protruding through tomentum. Leaf blades (crowded, internodes mostly 1-3, sometimes to 10 mm) linear-lanceolate, 3-7 cm × 1-5(-6) mm, bases subclasping, not decurrent, margins strongly revolute, faces bicolor, abaxial densely white-tomentose, adaxial green, densely stipitate-glandular. Heads in corymbiform arrays. Involucres broadly campanulate, 5-6 mm. Phyllaries in 5-7 series, bright white (opaque, dull), oblong to oblong-ovate, glabrous. Pistillate florets 66-85. Bisexual florets (6-14, California)29-44. Cypselae ridged, smooth. 2n = 28.
Flowering (Jul-)Aug-Nov(-Dec). Sandy or gravelly slopes, stream bottoms, arroyos, areas of oak-sycamore, oak-pine, to pine woodlands, commonly in riparian vegetation; 50-2100 m; Ariz., Calif., N.Mex.; Mexico (Baja California, Baja California Sur, Chihuahua, Durango, Sinaloa, Sonora).
Pseudognaphalium leucocephalum is similar to P. viscosum, which has shiny, hyaline, ovate-lanceolate phyllaries, 200-250 pistillate florets, (13-)16-29 bisexual florets, and papillate-roughened cypselae. Some plants of P. leucocephalum also appear to approach P. biolettii in general appearance, and it is possible that some of them may represent hybrids. Plants of P. biolettii differ from P. leucocephalum in their typically eglandular stems, broader, basally ampliate, clasping, more widely spaced, and less densely glandular leaves, and thinner, shiny phyllaries.
Duration: Perennial
Nativity: Native
Lifeform: Forb/Herb
General: Biennial to short-lived perennial herbs, 30-80 cm tall, from a taproot; stems 1-several per plant, erect, leafy, and persistently tomentose with dense, finely packed wool.
Leaves: Alternate and sessile; blades linear-oblanceolate (lower leaves) to narrowly linear-attenuate (upper leaves), 2-8 cm long by 2-6 mm wide, the upper surfaces green and puberulent-glandular, and the lower surfaces persistently and strongly white-tomentose.
Flowers: Flower heads discoid, numerous, arranged in corymbose panicles up to 20 cm broad; involucre (ring of bracts wrapped around the flower head) top-shaped, 6-7 mm high, 7-8 mm wide at anthesis, the bracts (phyllaries) well imbricated (overlapping and staggered like roof shingles) in 4-6 series, broadly ovate to oblong, dull pearly white, obtuse and minutely toothed at apex, the bases of outermost phyllaries embedded in loose wool; florets all discs, 4 mm long, the corollas white.
Fruits: Achenes 0.8 mm long, pale brown or straw-colored, smooth, dull; topped with a pappus of bristles which are distinct from each other, falling separately.
Ecology: Found in sandy washes, dry hillsides, and disturbed areas from 2,000-5,000 ft (610-1524 m); flowers July-October.
Distribution: CA, AZ, and NM; south to MEX.
Notes: In the desert southwest there are several species of Pseudognaphalium, Gnaphalium, and Gamochaeta, all similar and closely related genera. These genera are recognized by the white-wooly herbage; discoid flower heads more or less embedded in white wooly hairs; and tiny seeds (achenes) usually less than 1 mm long and topped with an early-deciduous pappus of bristles. P. leucocephalum is one of the more easily distinguished species in this group, with its strikingly white flower heads (the phyllaries in particular are completely white); tall, upright growth form up to 80 cm tall; large, roughly flat-topped panicles up to 20 cm wide; and very strongly bicolored leaves with vivid dark green upper faces and densely white tomentose lower faces.
Ethnobotany: Unknown for this species, but others in genus have medicinal use.
Etymology: Pseudognaphalium is false gnaphalium, the former genus name; leucocephalum means white-headed.
Synonyms: Gnaphalium leucocephalum
Editor: SBuckley 2010, AHazelton 2016
