Senna septemtrionalis
(smooth senna)

Preferred Common Name

• smooth senna

Other Scientific Names

• Adipera laevigata (Willd.) Britton & Wilson
• Cassia aurata Roxb.
• Cassia elegans Kunth
• Cassia floribunda sensu De Wit non Collad.
• Cassia laevigata Willd.
• Cassia quadrangularis Zoll. & Moritzi
• Cassia septemtrionalis Viv.
• Cassia vernicosa Clos
• Chamaecassia laevigata (Willd.) Link
• Chamaefistula laevigata (Willd.) G. Don
• Chamaesenna laevigata (Willd.) Pittier
• Senna aurata Roxb.

International Common Names

• English: arsenic bush; Brazilian buttercup; buttercup bush; dooleyweed; laburnum; senna; smooth leaved senna; yellow shower
• Spanish: leno hediondo (Spain); retama (Honduras)
• French: séné septentrional
• Chinese: guang ye jue ming

Local Common Names

• Brazil: canudo-de-pito
• Dominican Republic: brusca
• Fiji: winivinikau
• Guatemala: moco
• Indonesia/Java: senting; tayoomas; trembalon
• Indonesia/Nusa Tenggara: kasingsat; keetjandoong
• Madagascar: moco; retama; tsotsorinangatra; voandranomainty
• Mexico: cafecillo
• Nicaragua: café; coralillo; frijolillo; pico de pájaro
• Puerto Rico: hedionda macho
• South East Asia: bo cap nuroc

EPPO code

• CASLA (Cassia laevigata)

• Domain: Eukaryota
•     Kingdom: Plantae
•         Phylum: Spermatophyta
•             Subphylum: Angiospermae
•                 Class: Dicotyledonae
•                     Order: Fabales
•                         Family: Fabaceae
•                             Subfamily: Caesalpinioideae
•                                 Genus: Senna
•                                     Species: Senna septemtrionalis

Until the beginning of the 1980s the genus Cassia was considered to be a very large genus of over 500 species. Bentham (1871) wrote that three groups within the Cassia genus were so distinct from one another that any species can always be unequivocally allocated to one of them; some main distinctions included fruit structure, stamen structure and arrangement, and nodulation (Lock, 1988). However it was not until 1982 that Irwin and Barneby formally separated Cassia into three genera: Cassia L. emend. Gaertner, Senna Miller, and Chamaecrista Moench; Cassia now has only about 30 species, whereas Senna and Chamaecrista comprise about equal numbers of species, about 260 and 270 respectively (Irwin and Barneby, 1982; Sosef and Maesen, 1997). These three genera are now largely accepted and together make up subtribe Cassinae. Cassia and Senna differ principally in stamen organization, and in arid areas of Australia, taxonomic distinctions between and within the three genera are blurred by polyploidy, hybridization and apoximis (Lewis et al., 2005). In 1988 Lock presented new names and combinations for the Cassinae species in Africa, noting that “if Cassia were to continue to be used in its broad sense in Africa, there would be several species which would be consistently given different names in different continents” (Lock, 1988). 

Approximately 80% of the Senna genus’ 260 or so species occur in New World tropical and subtropical areas, extending into warm temperate and rarely into cool temperate areas of both hemispheres with species in Africa, Madagascar, Australia, and a few in southeastern Asia and Pacific islands (Irwin and Barneby, 1982; Lock, 1988; Wagner et al., 2014). 

There has been much taxonomic confusion over this species. The name Cassialaevigata was widely used for a long period, but when De Wit misapplied the name Cassia floribunda, that name came into general usage. Irwin and Barneby (1982) have now shown that the oldest name is Cassiaseptemtrionalis, and that the epithet floribunda should correctly be applied, as Senna × floribunda (Cav.) H.S. Irwin & Barneby, to the hybrid between S. septemtrionalis and S. multiglandulosa. (Brummitt et al., 2007) Historical data found under synonym names have been indicated in this datasheet.

Leafy shrubs or small trees 1-5 (-6.5) m tall. Leaflets 3-4 (5) pairs, the distal ones larger, broadly ovate to lanceolate, (3.5-) 4.5-10.5 cm long, (1.1-) 1.4-3.5 cm wide, glabrous, lower surface pale, apex acuminate or caudate, base obliquely rounded or cuneate, petiolar nectaries between all pairs or all but the distal pair of leaflets, none contiguous to pulvinus, the lowest one 1-2 mm long, stipules submembranous, narrowly lanceolate, 3-7 mm long, caducous. Flowers in racemes (1.5-) 2.5-8 cm long, pedicels (12-) 15-25 mm long, bracts sub-membranous, linear, lanceolate, or subulate, (1.5-) 2-4.5 mm long, caducous as pedicels begin to elongate; calyx lobes yellowish green, yellowish brown, or completely yellow, the outer ones relatively firm, ovate-elliptic, 4-6.5 mm long, the inner ones submembranous, oblong-obovate or suborbicular, 6.5-10 mm long; petals bright yellow, the standard obovate to obovate-flabellate, deeply emarginate, the others obovate, the longest petal 12-16 mm long; staminodes 3, obovate or suborbicular, (1.7-) 2-2.6 mm long; filaments of 4 median stamens 1.3-2.2 mm long, those of 2 abaxial stamens dilated, ribbon-like, 7-10.5 mm long, that of abaxial central stamen 2-4 mm long. Pods ascending on a stiff pedicel, chartaceous, cylindrical or obtusely quadrangular, 6-10.5 cm long, 0.8-1.1 cm wide, cavity moderately pulpy, divided into 2 parallel rows of of cells. Seeds oriented with broad face to the septum, olive or brown, compressed-obovoid, 3.6-4.9 mm long, constricted at the hilum, smooth or minutely pitted, without an areole (Wagner et al., 2014).

S. septemtrionalis has been cultivated for several centuries as an ornamental and certainly since pre-Columbian times for traditional medicinal uses in Mexico (Irwin and Barneby, 1982). The species has been widely introduced outside its native range of Central America to other tropical and temperate regions, where it is now naturalized in many places (Randall, 2012). It has been recorded as escaped from cultivation in India (Kumar and Sane, 2003). In Africa it was first collected in eastern Zimbabwe in 1906, where it was being used medicinally by local people (Brummitt et al., 2007). 

In the West Indies, Irwin and Barneby (1982) report that the species has been naturalized in Jamaica since the eighteenth century. It was certainly present in Jamaica before 1689, when Sir Hans Sloane collected a specimen as part of his voyage between 1687-1689 that resulted in the publications CatalogusPlantarum, 1696, and Natural History of Jamaica, 1707 (UK Sloane Herbarium Specimen 737). The species’ native status in Cuba and Puerto Rico is uncertain, but it was observed in Puerto Rico as early as 1881 and was included (as Cassia laevigata Willd.) in Bello’s Flora of Puerto Rico (Bello Espinosa, 1881; Acevedo-Rodriguez and Strong, 2012). The presence of this species was also reported (as C. laevigata Willd.) between 1903-1911 in Jamaica, Martinique, tropical America, western tropical Africa, and Australasia (Urban, 1905). Other places with reports of the species (date of introduction unknown, but after the eighteenth century) include the Dominican Republic (naturalized); Martinique, Barbados and the Gulf of Panama (weedy or cultivated only); upland Colombia, Pacific Peru, Distrito Federal in Brazil, and gardens in Argentina and Chile (collected infrequently and unknown status but unlikely to be wild); tropical Africa, India, Sri Lanka, Malay Penninsula, Java and Sumatra, eastern Australia and Pacific islands including Fiji and Hawaii (long established); and Florida and tropical North America (widespread in horticulture and under glass) (Irwin and Barneby, 1982).

Soil reaction

• acid
• alkaline
• neutral

Soil texture

• light
• medium

In addition to repeated intentional introduction and cultivation of the species across tropical and subtropical regions of the world for ornamental, agroforestry, and food purposes, S. septemtrionalis has also been shown to have escaped cultivation and been accidentally introduced to the wild (Sosef and Maesen, 1997; Kumar and Sane, 2003; Brummitt et al., 2007; Weeds of Australia, 2014). The species reproduces mainly by seeds, which are numerous and easily dispersed by water or by mud carried by humans, animals and machinery, or as a contaminant in agricultural produce (Weeds of Australia, 2014). It can be further spread by birds or through mass movement of soil and flood debris (West, 2001).

Despite being widely cultivated as an ornamental as well as a shade and hedge plant and green manure for agroforestry purposes, S. septemtrionalis has been shown to have a negative impact on its local environment due to its rapid maturity rate, abundant seed production, long-lived seed bank, and multiple biotic and abiotic vectors for seed dispersal (West, 2003). The species was identified as the most widespread and difficult to remove invasive species on Raoul Island, New Zealand, and is considered an environmental and agricultural weed in the Global Compendium of Weeds (West, 2003; Randall, 2012). The seeds and other plant parts are also suspected to be mildly toxic to humans and grazing animals, but there is insufficient evidence to substantiate the claims; it is also possible that the negative health effects can be negated by cooking the pulses before eating (Sosef and Maesen, 1997; CANBR, 2014).

• Proved invasive outside its native range
• Has a broad native range
• Abundant in its native range
• Tolerates, or benefits from, cultivation, browsing pressure, mutilation, fire etc
• Pioneering in disturbed areas
• Highly mobile locally
• Benefits from human association (i.e. it is a human commensal)
• Long lived
• Fast growing
• Has high reproductive potential
• Has propagules that can remain viable for more than one year
• Reproduces asexually

• Damaged ecosystem services
• Ecosystem change/ habitat alteration
• Negatively impacts agriculture
• Reduced native biodiversity
• Threat to/ loss of endangered species
• Threat to/ loss of native species

• Competition - monopolizing resources
• Rapid growth

• Highly likely to be transported internationally accidentally
• Highly likely to be transported internationally deliberately

S. septemtrionalis has been cultivated as an ornamental plant for over 200 years and, since pre-Columbian times, used for folk medicine, so the primary range of dispersal has been thereby modified and lost to view (Irwin and Barneby, 1982). It is grown in plantations as a shade tree and as green manure, and in Java, Ethiopia and other places it is valued as a hedge plant. In Madagascar the seeds are crushed and added to coffee as a Malagasy beverage, and in Guatemala they are used as a coffee substitute. The unripe seeds, young shoots, and the leaves are eaten cooked in Sumatra and parts of India (Sosef and Maesen, 1997; Puy et al., 2002; Hanelt et al., 2001).