Flora of North America species comparison

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Pseudognaphalium leucocephalum

Pseudognaphalium thermale

white cudweed, white rabbit-tobacco

northwestern rabbit-tobacco, slender cudweed, slender false cudweed, small head cudweed, Wright's cudweed
Habit Biennials or short-lived perennials, 30–60 cm; taprooted. Perennials, (20–)30–70 cm; taprooted.
Stems

densely and persistently white-tomentose, usually with stipitate-glandular hairs protruding through tomentum.

loosely tomentose, not glandular.
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.

blades narrowly oblanceolate, 3–8 cm × 3–6 mm (gradually smaller distally, becoming linear), bases not clasping, decurrent 5–14 mm, margins flat, faces concolor, loosely tomentose, sessile-glandular beneath tomentum.
Involucres

broadly campanulate, 5–6 mm.

turbinate-campanulate, (4–)5–6 mm.
Pistillate florets

66–85.

35–55.
Bisexual florets

(6–14, California)29–44.

(2–)4–7.
Phyllaries

in 5–7 series, bright white (opaque, dull), oblong to oblong-ovate, glabrous.

in 3–4(–5) series, whitish (hyaline or opaque, usually shiny, sometimes dull), ovate to ovate-oblong (outer broadly acute, inner rounded-apiculate), glabrous.
Heads

in corymbiform arrays.

in loose to dense, corymbiform to paniculiform arrays.
Cypselae

ridged, smooth.

ridged, densely papillate-roughened.
2n

= 28.

Pseudognaphalium leucocephalum

Pseudognaphalium thermale
Phenology Flowering (Jul–)Aug–Nov(–Dec). Flowering Jun–Sep(–Oct).
Habitat Sandy or gravelly slopes, stream bottoms, arroyos, areas of oak-sycamore, oak-pine, to pine woodlands, commonly in riparian vegetation Dry, sandy road banks, roadside ditches, streambeds and banks, lakeshores, granitic sand, open woods of yellow pine, Jeffrey pine, red fir, Douglas fir, mixed conifer, and mixed evergreen
Elevation 50–2100 m (200–6900 ft) (50–)300–2300(–2500) m ((200–)1000–7500(–8200) ft)
Distribution
from FNA
AZ; CA; NM; Mexico (Baja California, Baja California Sur, Chihuahua, Durango, Sinaloa, Sonora)
[WildflowerSearch map]
[BONAP county map]
from FNA
CA; ID; MT; NV; OR; UT; WA; WY; AB; BC
[WildflowerSearch map]
Discussion

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.

(Discussion copyrighted by Flora of North America; reprinted with permission.)
Source FNA vol. 19, p. 423. FNA vol. 19, p. 419.
Parent taxa Asteraceae > tribe Gnaphalieae > Pseudognaphalium Asteraceae > tribe Gnaphalieae > Pseudognaphalium
Sibling taxa
P. arizonicum, P. austrotexanum, P. beneolens, P. biolettii, P. californicum, P. canescens, P. helleri, P. jaliscense, P. luteoalbum, P. macounii, P. micradenium, P. microcephalum, P. obtusifolium, P. pringlei, P. ramosissimum, P. roseum, P. saxicola, P. stramineum, P. thermale, P. viscosum
P. arizonicum, P. austrotexanum, P. beneolens, P. biolettii, P. californicum, P. canescens, P. helleri, P. jaliscense, P. leucocephalum, P. luteoalbum, P. macounii, P. micradenium, P. microcephalum, P. obtusifolium, P. pringlei, P. ramosissimum, P. roseum, P. saxicola, P. stramineum, P. viscosum
Synonyms Gnaphalium leucocephalum Gnaphalium thermale, Gnaphalium canescens subsp. thermale, Gnaphalium johnstonii, Gnaphalium microcephalum var. thermale, Gnaphalium microcephalum subsp. thermale, P. canescens subsp. thermale, P. microcephalum var. thermale
Name authority (A. Gray) Anderberg: Opera Bot. 104: 147. (1991) (E. E. Nelson) G. L. Nesom: Sida 21: 781. (2004)
Web links 
Unless otherwise noted, all data comes from the online version of the Flora of North America, who have made most of their content available via a Creative Commons license (CC BY 4.0).



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