Bighead Pygmycudweed

Intermediates between the two varieties of Diaperia prolifera occur where their ranges meet in central Texas and central Oklahoma. The strictly dichasiform or pseudo-polytomous branching pattern of D. prolifera is distinctive and diagnostic within the genus. Specimens of D. prolifera from introductions around a wool mill in South Carolina (G. L. Nesom 2004c, as Evax prolifera) are as yet undetermined to variety and are not included in the distributions below.

Plants grayish green to silvery, 3–15 cm, sericeous to lanuginose. Stems mostly 2–10; branches proximal and distal (distal opposite or, sometimes, appearing alternate when unequal), rarely none. Leaves: largest 7–15 × 2–4 mm; capitular leaves subtending glomerules, also visible between and surpassing heads. Heads in strictly dichasiform or pseudo-polytomous arrays (sometimes appearing monochasiiform), cylindric to ± ellipsoid, 3.5–4.5 mm, heights 2–3 times diams. Receptacles broadly or narrowly conic, 0.4–0.6 mm or ± 0.9–1.1 mm, heights 0.5–0.7 or 2–2.4 times diams. Pistillate paleae imbricate, longest 2.5–4 mm. Staminate paleae ± 3, apices erect to somewhat spreading, ± plane. Functionally staminate florets 2–4; ovaries partly developed, 0.4–0.6 mm; corollas hidden in heads, actinomorphic, 1.4–2 mm, glabrous, lobes equal. Bisexual florets 0. Cypselae ± angular, obcompressed, mostly 0.9–1.2 mm.

Evax prolifera Nuttall ex de Candolle in A. P. de Candolle and A. L. P. P. de Candolle, Prodr. 5: 459. 1836

Diaperia prolifera, common name big-head rabbit-tobacco, is a plant species native to the central part of the United States from Montana to New Mexico to Alabama. It prefers dry, open areas.

Diaperia prolifera is an annual herb up to 15 cm (6 inches) tall, grayish green to silvery because of thick woolly pubescence. The stem branches above ground, with leaves up to 15 mm long. Flower heads are usually produced one at a time, but occasionally in groups of 2–3.

Varieties

Two varieties are generally recognized, intergrading in their region of overlap in Texas and Oklahoma:

Diaperia prolifera var. prolifera, grayish to green - Alabama, Arkansas, Colorado, Kansas, Louisiana, Mississippi, Missouri, Montana, Nebraska, New Mexico, Oklahoma, Texas, South Dakota, Wyoming Diaperia prolifera var. barnebyi Morefield, silvery white - New Mexico, Oklahoma, Texas