Packera tridenticulata

(Rydberg) W. A. Weber & Á. Löve

Phytologia 49: 48. 1981.

Common names: Threetooth ragwort
Basionym: Senecio tridenticulatus Rydberg Bull. Torrey Bot. Club 27: 175, plate 5, fig. 12. 1900 Senecio compactus (A. Gray) Rydberg 1894
Synonyms: Senecio acutidens Rydberg Senecio densus Greene Senecio oblanceolatus Rydberg
Treatment appears in FNA Volume 20. Treatment on page 601. Mentioned on page 573, 593, 602.

Perennials, 10–30+ cm; taprooted (caudices ascending to erect). Stems 1 or multiple, clustered, usually glabrous, rarely sparsely floccose-tomentose, leaf axils sometimes tomentose. Basal leaves (and proximal cauline, relatively thick and turgid) petiolate; blades lanceolate or narrowly oblanceolate, 20–40+ × 5–15 mm, bases tapering, margins usually entire, sometimes sub-pinnatisect (apices subentire or dentate). Cauline leaves gradually reduced (± petiolate or sessile). Heads 4–15+ in corymbiform arrays. Peduncles bracteate, glabrous or sparsely tomentose. Calyculi inconspicuous. Phyllaries 13 or 21, green, 6–10 mm, sparsely tomentose proximally, glabrous distally. Ray florets 8–10(–13); corolla laminae 5–8+ mm. Disc florets 45–60+; corolla tubes 3–3.5 mm, limbs 4–5 mm. Cypselae 1.5–2.5 mm, glabrous or sparsely hirtellous on ribs; pappi 5–6 mm. 2n = 46.

Phenology: Flowering late May–early Jul.
Habitat: Open, dry areas, roadsides, gravelly or sandy slopes, short-grass prairies or sagebrush scrubs
Elevation: 1000–2000 m



Colo., Kans., Nebr., N.Mex., N.Dak., Okla., S.Dak., Tex., Wyo.


Packera tridenticulata is found throughout the central High Plains, in the foothills of the Rocky Mountains, and in high valleys to the west of the Rocky Mountain front. It tends to grow in clumps; the multiple stems arise from well-developed taproots. It apparently hybridizes with P. neomexicana var. mutabilis where their ranges overlap.

Selected References


Lower Taxa

... more about "Packera tridenticulata"
Debra K. Trock +
(Rydberg) W. A. Weber & Á. Löve +
Senecio tridenticulatus +  and Senecio compactus +
Threetooth ragwort +
Colo. +, Kans. +, Nebr. +, N.Mex. +, N.Dak. +, Okla. +, S.Dak. +, Tex. +  and Wyo. +
1000–2000 m +
Open, dry areas, roadsides, gravelly or sandy slopes, short-grass prairies or sagebrush scrubs +
Flowering late May–early Jul. +
Senecio acutidens +, Senecio densus +  and Senecio oblanceolatus +
Packera tridenticulata +
species +