Isocoma tenuisecta

Herbage minutely hispidulous to hirtellous or sparsely puberulous (at least distal stems), not resinous. Leaf blades oblong-oblanceolate, 20-35 mm, margins pinnatifid (lobes spreading at right angles, linear to filiform). Involucres 4-6.5 × 2-2.8 mm. Phyllary apices with small, sharply delimited, green resinous area, not aristate, often distinctly thickened and approaching resin pockets, usually gland-dotted. Florets 8-12(-15); corollas 4.5-6 mm. Cypsela ribs not forming hornlike extensions.

Flowering Sep-Nov. Sandy or gravelly flats and hills, grasslands, usually matorral or Larrea stands; 700-1600 m; Ariz., N.Mex.; Mexico (Sonora).

Some plants approach Isocoma acradenia var. acradenia in leaf and phyllary morphology in southern Arizona, where the ranges of the two taxa overlap.

FNA 2006, Benson and Darrow 1981, Kearney and Peebles 1969

Common Name: burroweed Duration: Perennial Nativity: Native Lifeform: Subshrub General: Shrub to sub-shrub, 0.3-1 m tall and 1 m wide; bark of larger branches gray. Leaves: Alternate, dark-green to gray, glandular, pinnately cleft into four to eight linear acute lobes. Main axis of leaves 2-3.5 cm long, about 1 mm broad, divisions 0.2-2 cm long, about 1 mm broad. Flowers: Yellow, discoid, with no ray flowers, arranged into dense terminal clusters. Flowers dry and turn a light brown but remain on stems. Bracts are glandular as well. Fruits: Cypselae, with the ribs not forming hornlike extensions. Ecology: Found on dry slopes, mesas, and alluvial plains from 2,000-5,500 ft (610-1676 m); flowers from August-October. Notes: Significant invader of depleted rangelands, often coming to constitute the principle cover. Susceptible to drought and is not fire tolerant. This plant is toxic to livestock. Ethnobotany: No known uses. Etymology: Isocoma is from the greek meaning -an equal hair-tuft- referring to flowers, while tenuisecta means thinly or narrowly cut. Synonyms: Happlopappus tenuisectus Editor: SBuckley, 2010