Perennials or subshrubs, to 100 cm. Stems erect, puberulent to glabrate. Leaves opposite; pet-ioles 3-15 mm; blades narrowly to broadly lanceolate, (2-)3-7 × 0.5-1.5 cm, margins coarsely and remotely serrate, apices long-acuminate, abaxial faces sparsely pubescent. Heads clustered. Peduncles 2-6 mm, puberulent. Involucres 2.5-3 mm. Phyllaries: apices acute, abaxial faces puberulent-hispidulous. Corollas white, lobes sparsely hispid-villous. Cypselae glabrous. Flowering Mar-May. Rocky slopes, crevices, gravelly, sandy streambeds, pine-oak woodlands; 1000-1800 m; Ariz.; Mexico. Ageratina paupercula is recognized by its early spring flowering, relatively small and usually narrowly lanceolate and acuminate leaves, relatively small heads in clusters, and relatively small (1.2-1.4 mm versus mostly 2-3 mm in other species), glabrous cypselae.

FNA 2006, Kearney and Peebles 1969

Duration: Perennial Nativity: Native Lifeform: Forb/Herb General: Perennial herbs or subshrubs to 1 m tall; stems erect, puberulent to glabrate. Leaves: Opposite and petiolate, the petioles to 1.5 cm; blades to 7 cm long, narrowly lanceolate with a long-acuminate apex and serrate margins, sparsely pubescent on the lower surface. Flowers: Flower heads discoid, arranged in clusters, on 2-6 mm peduncles; involucre (the ring of bracts surrounding each flower head) 3 mm high, the bracts in 2-3 series, subequal, acuminate, pubescent on the outer surface; flowers are all discs (radial, bisexual, with a 5-lobed corolla), the corollas white, sparsely hispid-villous, with protruding stamens. Fruits: Achenes 1 mm, glabrous. Ecology: Found in canyons near streams, from 3,500-5,000 ft (1067-1524 m); flowers March-May. Distribution: s AZ and Sonora, MEX Notes: The keys to this species are the pubescent phyllaries (involucral bracts); the narrowly lanceolate leaves, 3 to 5 times as long as wide; and the flowering heads and achenes (seeds) which are relatively small compared to other Ageratina spp. Note also that this species flowers in the spring; other Ageratina commonly flower in the summer. Ethnobotany: Unknown Etymology: Ageratina is a dimunitive of Ageratum, which is from Greek ageratons for not growing old, while paupercula means poor. Synonyms: Eupatorium pauperculum, Kyrstenia paupercula Editor: SBuckley 2010, AHazelton 2015