The green links below add additional plants to the comparison table. Blue links lead to other Web sites.
enable glossary links

butterweed

threetooth ragwort

Habit Annuals or biennials, 20–70+ cm; fibrous-rooted (caudices relatively short, weak). Perennials, 10–30+ cm; taprooted (caudices ascending to erect).
Stems

1 (striated, frequently hollow, often pink- to purple-tinged), glabrous or leaf axils sparsely tomentose.

1 or multiple, clustered, usually glabrous, rarely sparsely floccose-tomentose, leaf axils sometimes tomentose.

Basal leaves

(and proximal cauline) obscurely petiolate;

blades obovate to oblanceolate, sometimes lyrate (lateral lobes to 5 pairs, terminal lobes larger than laterals), 50–150+ × 10–30+ mm, bases tapering, ultimate margins crenate to irregularly undulate.

(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 (weakly clasping, similar to basal).

gradually reduced (± petiolate or sessile).

Peduncles

bracteate, glabrous or bases tomentose.

bracteate, glabrous or sparsely tomentose.

Ray florets

(8–)13;

corolla laminae 7–9 mm.

8–10(–13);

corolla laminae 5–8+ mm.

Disc florets

35–50+;

corolla tubes 2.5–3.5 mm, limbs 2–3 mm.

45–60+;

corolla tubes 3–3.5 mm, limbs 4–5 mm.

Phyllaries

(13–)21, green, 5–7 mm, glabrous.

13 or 21, green, 6–10 mm, sparsely tomentose proximally, glabrous distally.

Calyculi

conspicuous (bractlets 2.5–4 mm).

inconspicuous.

Heads

8–30+ in umbelliform or cymiform arrays (robust plants with multiple arrays).

4–15+ in corymbiform arrays.

Cypselae

1–1.5 mm, sparsely hirtellous on ribs or glabrous;

pappi 3–4 mm.

1.5–2.5 mm, glabrous or sparsely hirtellous on ribs;

pappi 5–6 mm.

2n

= 46.

= 46.

Packera glabella

Packera tridenticulata

Phenology Flowering (Feb–)mid Mar–late May. Flowering late May–early Jul.
Habitat Open wet areas, edges of woodlands, stream banks, roadsides, meadows, marshes, fallow fields Open, dry areas, roadsides, gravelly or sandy slopes, short-grass prairies or sagebrush scrubs
Elevation 0–600 m (0–2000 ft) 1000–2000 m (3300–6600 ft)
Distribution
from FNA
AL; AR; FL; GA; IL; IN; KS; KY; LA; MO; MS; NC; NE; OH; OK; SC; TN; TX
[WildflowerSearch map]
[BONAP county map]
from FNA
CO; KS; ND; NE; NM; OK; SD; TX; WY
[WildflowerSearch map]
Discussion

Packera glabella is common and almost weedy in wet, partially shaded places. The hollow, striated stems of P. glabella are distinctive.

(Discussion copyrighted by Flora of North America; reprinted with permission.)

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.

(Discussion copyrighted by Flora of North America; reprinted with permission.)

Source FNA vol. 20, p. 588. FNA vol. 20, p. 601.
Parent taxa Asteraceae > tribe Senecioneae > Packera Asteraceae > tribe Senecioneae > Packera
Sibling taxa
P. anonyma, P. antennariifolia, P. aurea, P. bernardina, P. bolanderi, P. breweri, P. cana, P. cardamine, P. castoreus, P. clevelandii, P. contermina, P. crocata, P. cymbalaria, P. cynthioides, P. debilis, P. dimorphophylla, P. eurycephala, P. fendleri, P. flettii, P. franciscana, P. ganderi, P. greenei, P. hartiana, P. hesperia, P. hyperborealis, P. indecora, P. ionophylla, P. layneae, P. macounii, P. malmstenii, P. millefolium, P. millelobata, P. multilobata, P. musiniensis, P. neomexicana, P. obovata, P. ogotorukensis, P. pauciflora, P. paupercula, P. plattensis, P. porteri, P. pseudaurea, P. quercetorum, P. sanguisorboides, P. schweinitziana, P. spellenbergii, P. streptanthifolia, P. subnuda, P. tampicana, P. texensis, P. tomentosa, P. tridenticulata, P. werneriifolia
P. anonyma, P. antennariifolia, P. aurea, P. bernardina, P. bolanderi, P. breweri, P. cana, P. cardamine, P. castoreus, P. clevelandii, P. contermina, P. crocata, P. cymbalaria, P. cynthioides, P. debilis, P. dimorphophylla, P. eurycephala, P. fendleri, P. flettii, P. franciscana, P. ganderi, P. glabella, P. greenei, P. hartiana, P. hesperia, P. hyperborealis, P. indecora, P. ionophylla, P. layneae, P. macounii, P. malmstenii, P. millefolium, P. millelobata, P. multilobata, P. musiniensis, P. neomexicana, P. obovata, P. ogotorukensis, P. pauciflora, P. paupercula, P. plattensis, P. porteri, P. pseudaurea, P. quercetorum, P. sanguisorboides, P. schweinitziana, P. spellenbergii, P. streptanthifolia, P. subnuda, P. tampicana, P. texensis, P. tomentosa, P. werneriifolia
Synonyms Senecio glabellus, Senecio carolinianus, Senecio densiflorus, Senecio lobatus, Senecio lyratus, Senecio mississipianus Senecio tridenticulatus, Senecio acutidens, Senecio compactus, Senecio densus, Senecio oblanceolatus
Name authority (Poiret) C. Jeffrey: Kew Bull. 47: 101. (1992) (Rydberg) W. A. Weber & Á. Löve: Phytologia 49: 48. (1981)
Web links