Senna corymbosa
Senna obtusifolia
Argentine senna, Argentine wild sensitive plant
blunt leafed senna, Chinese senna, Java-bean, sickle-pod wild senna, sicklepod
mesophyllous, 5.5–9.5 cm, glabrous or glabrate;
stipules caducous;
extrafloral nectary 1, between first leaflet pair, sessile or short-stipitate;
leaflet pairs 3, blades oblong-lanceolate, 25–60 × 5–14 mm.
mesophyllous, 3.5–17 cm, pallid green, slightly and finely hairy or glabrous;
stipules caducous;
extrafloral nectary 1, usually between first leaflet pair, rarely also between second, sessile or shortly stipitate;
leaflet pairs 3, blades obovate to cuneate-obovate or broadly cuneate-oblanceolate, 17–65 × 10–40 mm.
4–18-flowered;
bracts caducous.
usually 1 or 2(or 3)-flowered;
bracts caducous.
13–23 mm.
7–28 mm.
monosymmetric;
calyx brownish to greenish yellow;
corolla golden yellow, longest petal 8–16 mm;
androecium heterantherous, stamens 7, middle stamens 1/2 as long as abaxial or smaller, staminodes 3;
anthers of middle stamens to 3.6–4.8 mm, of abaxial stamens 5.2–6.5 mm, dehiscing by nearly U-shaped pore, apical appendage inconspicuous;
gynoecium incurved, ovules 34–50;
ovary hairy;
style slightly incurved.
asymmetric, enantiostylous;
calyx pale green;
corolla pale yellow, longest petal 9–15 mm, 1 lower petal conspicuously larger;
androecium heterantherous, stamens 7, middle stamens 1/2 as long as abaxial or smaller, staminodes 3;
anthers of middle stamens 1–2.8 mm, of abaxial stamens 2–5 mm, dehiscing by U-shaped slit, apical appendage inconspicuous, cupped;
gynoecium incurved, ovules 16–38;
ovary hairy;
style incurved.
somewhat pendulous, cylindrical, straight, 40–120 × 6–10 mm, corrugated over seeds, indehiscent.
erect or curved downward, flat, straight, 60–180 × 2.5–6 mm, faintly corrugated over seeds, indehiscent.
dull brown or dark reddish brown, obliquely obovoid or oblong-ellipsoid.
dark reddish brown, rhomboid or subcylindroid-oblong.
= 28.
= 24, 26, 28.
Senna corymbosa
Senna obtusifolia
Senna corymbosa has been cultivated for over two centuries and is a common ornamental in many botanical gardens worldwide; it has become naturalized in warmer western Europe and South Africa (H. S. Irwin and R. C. Barneby 1982).
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Senna obtusifolia is one of the most widespread weedy sennas native to the Americas (H. S. Irwin and R. C. Barneby 1982) and is probably naturalized circumtropically. The species is considered a noxious weed in many countries, posing problems especially for agriculture; it is able to completely invade pastures by dominating grass species, it strongly competes with crops, affecting yields negatively, and, although generally unpalatable to stock, if eaten, it is toxic to cattle. For these reasons, in Australia S. obtusifolia is designated as potentially of national concern, and authorities estimate that this invader can lead properties to become unproductive (Weeds of Australia, www.environment.gov.au/cgi-bin/biodiversity/invasive/weeds/weedsearch.pl; Land Protection, www.nrw.qld.gov.au/factsheets/pdf/pest/pp18.pdf). In the flora area, its range of distribution appears to have expanded from five southern and southeastern states in the early 1980s (Florida, Kentucky, Missouri, Texas, and Virginia; Irwin and Barneby) to currently almost half of the states. Although a few specimens were collected as far north as Nebraska and Wisconsin, it is not known to be established in those states.
Senna tora (Linnaeus) Roxburgh (Cassia tora Linnaeus) is sometimes considered synonymous with S. obtusifolia. However, due to differences in length and curvature of the fruit and in length of the petiole and pedicel, B. R. Randell and B. A. Barlow (1998) considered it distinct. H. S. Irwin and R. C. Barneby (1982) observed a range rather than distinct categories in the measures and shapes of these traits, and only molecular phylogenetic and biogeographic studies accompanied by morphometric analyses may definitively solve this taxonomic dilemma.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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