Heterotheca stenophylla var. angustifolia

Distal mid stems moderately to densely hispido-strigose, eglandular or sparsely stipitate-glandular. Leaves pale green to gray-green, faces moderately to ± densely hispido-strigose (21-60 hairs/mm²; hairs rarely broad-based, pustulate), eglandular to sparsely glandular; distal cauline linear to narrowly oblanceolate, rarely broadly so, (14-)18.7(-30) × (2-)2.6-4.5(-6) mm, margins proximally long-hispido-strigose, sometimes cilia numerous along whole length, faces sparsely to moderately hispido-strigose, eglandular. Phyllary faces usually moderately strigose, eglandular. 2n = 36.

Flowering May-Aug(-Oct). Sandy and gravelly soils, sandy loam, sandy gypsiferous soil, prairies, hillsides, pastures, open areas by oak wooded ravines, disturbed slopes, grasslands, stabilized dunes; 300-1400 m; Colo., Kans., Nebr., N.Mex., Okla., S.Dak., Tex.

Variety angustifolia grows in the Great Plains from central Texas and New Mexico to eastern Colorado and southern South Dakota. Triploid chromosome counts from putative intervarietal hybrids have been reported. Variety angustifolia usually has densely hispid distal mid stems with many long-spreading hairs and densely hispido-strigose, eglandular leaves and phyllaries. The most densely hairy individuals are not always easily distinguished from sympatric forms of Heterotheca canescens. Both diploid and tetraploid individuals of H. canescens usually have more than 100 hairs/mm ² of leaf face versus less than 60 hairs/mm ² in both varieties of H. stenophylla. The difference manifests itself in silvery gray-green versus green (bright to dark) or gray-green leaves, respectively. Stems of H. villosa usually have relatively longer nodes and a less densely leafy appearance. The leaves can be as densely hairy. Variety angustifolia historically has been included in H. villosa.