Senna roemeriana |
Senna occidentalis |
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Roemer senna, twoleaf senna, twoleaf wild sensitive plant |
coffee senna, septicweed |
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Habit | Herbs, perennial, to 0.7 m. Leaves slightly sclerophyllous, 2.5–9.5 cm, hairy; stipules caducous; extrafloral nectary 1, between leaflet pair, shortly stipitate; leaflet pairs 1, blades lanceolate-oblong or lanceolate, 20–70 × 4–14 mm. | Herbs, perennial, bushy, to 2.2 m; branches dark green and blackish. |
Leaves | mesophyllous, 11–26 cm, glabrous or glabrate; stipules caducous; extrafloral nectary 1, base of petiole, sessile or subsessile; leaflet pairs 4 or 5(or 6), blades lanceolate- or ovate-acuminate, 45–100 × 12–38 mm. |
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Racemes | 1–5-flowered; bracts caducous. |
usually (1 or)2–5-flowered; bracts caducous, longer than bud, often blackish green. |
Pedicels | 9–16 mm. |
8–21 mm. |
Flowers | monosymmetric; calyx caducous, pale green; corolla yellow or orange-yellow, longest petal 12–17 mm; androecium not heterantherous, stamens 7, staminodes 3; anthers 2.2–3.3 mm, dehiscing by 1 apical pore, apical appendage 0; gynoecium nearly linear, ovules 22–40; ovary densely hairy; style slightly incurved. |
monosymmetric; calyx pinkish or fuscous; corolla yellow, longest petal 12–17 mm; androecium heterantherous, stamens 6, staminodes 3 + 1; anthers of middle stamens 3.2–5.2 mm, of abaxial stamens 4.9–6.6 mm, elongated beyond pores, dehiscing by U-shaped pore, apical appendage linguiform, thickened; gynoecium incurved, ovules 40–60; ovary densely hairy; style slightly incurved. |
Legumes | erect, subcylindrical, straight or slightly curved, 20–35 × 4.5–6.5 mm, corrugated over seeds, dehiscing apically downward. |
ascending, flat, slightly curved or straight, linear, 80–135 × 6.5–9.5 mm, corrugated over seeds, dehiscent. |
Seeds | brown or pinkish brown, paddle-shaped or pyriform. |
olive green or brownish, obovoid. |
2n | = 28. |
= 26, 28. |
Senna roemeriana |
Senna occidentalis |
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Phenology | Flowering spring–early fall. | Flowering mid summer–early winter. |
Habitat | Mesquite grasslands, chaparral, draws in shortgrass prairies, barren hillsides, desert washes, roadsides. | Disturbed habitats, waste places, roadsides. |
Elevation | 100–2000 m. (300–6600 ft.) | 0–1200 m. (0–3900 ft.) |
Distribution |
NM; OK; TX; Mexico (Chihuahua, Coahuila, Nuevo León)
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AL; AR; FL; GA; IA; IL; IN; KS; LA; MA; MD; MO; MS; NC; NY; OK; SC; TN; TX; VA; Mexico; Central America; South America; West Indies [Introduced in North America; introduced also in tropical and subtropical Eurasia, Africa, Australia]
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Discussion | Although Senna occidentalis is probably native to the tropical New World, the species is now weedy in so many countries worldwide, including also other parts of the New World, that the exact range of its geographic distribution as a native is a matter of speculation (H. S. Irwin and R. C. Barneby 1982). In the flora area, it is considered as naturalized (R. Kral et al. 2012; R. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
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Source | FNA vol. 11. | FNA vol. 11. |
Parent taxa | Fabaceae > subfam. Caesalpinioideae (excluding Mimosoid clade) > Senna | Fabaceae > subfam. Caesalpinioideae (excluding Mimosoid clade) > Senna |
Sibling taxa | ||
Synonyms | Cassia roemeriana, Earleocassia roemeriana | Cassia occidentalis, Ditremexa occidentalis |
Name authority | (Scheele) H. S. Irwin & Barneby: Mem. New York Bot. Gard. 35: 282. (1982) | (Linnaeus) Link: Handbuch 2: 140. (1829) |
Web links |