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Siamese senna (Senna siamea)


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Common names 

Siamese senna, Bombay blackwood, cassod tree, ironwood, Kassaof tree, kassod tree, kassod tree, pheasantwood, Siamese acacia, Thai cassia; Thai copper pod, Thailand shower, yellow cassia [English]; bois perdrix, cassia [French]; cásia-do-Siao, cassia-siamesa, cássia-siamica [Portuguese]; casia amarilla, casia de Siam, casia siamea, flamboyán amarillo [Spanish]; manga konnei, vakai, wa [Tamil]; johar [Bahasa Indonesia]; कसोद [Hindi]; 鐵刀木 [Chinese]; タガヤサン [Japanese] মিনজিরি [Bengali]; ขี้เหล็ก [Thai]; muồng đen, muồng xiêm [Vietnamese]


Cassia arayatensis sensu Naves, Cassia arborea Macfad., Cassia florida Vahl, Cassia gigantea DC., Cassia siamea Lam., Cassia siamea Lam. var. puberula Kurz, Cassia sumatrana Roxb., Cassia sumatrana DC. Chamaefistula gigantea G. Don, Sciacassia siamea (Lam.) Britton & Rose, Senna sumatrana (DC.) Roxb. (ILDIS, 2018).

Taxonomic information 

While Senna siamea is now the recognized scientific name, it used to be widely referred to as Cassia siamea.

Related feed(s) 

Siamese senna (Senna siamea (Lam.) H.S. Irwin & Barneby) is a medium-sized, fast-growing tree legume that is used as fodder and browse for ruminant livestock in tropical lowlands. Its fruits and pods are edible and its wood can be used for fuel or for making poles and furniture. Siamese senna provides many environmental services and is used as an ornamental.


Senna siamea is an evergreen, medium-sized, many-branched tree legume. It reaches 10-12 m on average, rarely exceeding 20 m, and can exceptionnally reach 30 m (Rojas-Sandoval et al., 2013). Its root system consists in few thick and deep roots and in a dense mat of rootlets that spreads rapidly (up to 7 m in one year) (Orwa et al., 2009). Siamese senna is easily uprooted by strong winds (Rojas-Sandoval et al., 2013). The trunk is straight, up to 30 cm in diameter, with a rounded and dense crown. The bark is gray to light brown, becoming fissured with age (Orwa et al., 2009. The leaves are alternate, 10-35 cm long, pinnatelay compound with 6-14 pairs of leaflets. Leaflets are oblong in shape, 3-7 cm long x 1.2-2 cm broad, dark green in colour with a midrib ending in a short bristle (Orwa et al., 2009). The inflorescence is upright, borne on peduncles at the apex of the branches. It is a 30- 60 cm long x 13 cm broad panicle of bright yellow pentamerous flowers, 3 cm in diameter (Orwa et al., 2009). The pods are numerous, long, narrow, 5-25 cm long x 12-20 mm broad, flat, dark brown, dehiscent and compressed between seeds. The seeds are numerous (20-30), bean-shaped, shiny, dark brown, 8 mm long, with distinct areole (Orwa et al., 2009). There are 35,000 to 41,000 seeds per kg (Rojas-Sandoval et al., 2013).


Senna siamea is grown for fodder and browsed by livestock, though the extent of this use is unclear: it has be described both as occasional (Göhl, 1982) and widespread (Orwa et al., 2009). In any case, it should be used only for feeding ruminants, as its leaves, flowers and pods foliage contains alkaloids and anti-nutritional compounds that are toxic to non-ruminants such as pigs and poultry, which should be kept away from the plantations (Orwa et al., 2009). The limited information available seem to indicate that it can be used safely for rabbits (see the Rabbit section below). The fruits and leaves are used for food as vegetables or in curries but cooking water should be replaced 3 times to remove undesirable substances. Though it produces some smoke, the wood can be used as fuelwood or to make high grade charcoal. The timber makes hard to very hard wood that is resistant to termites. While difficult to work with, it used to make poles, posts, bridges, mine timbers and the heartwood for cabinet-making joinery and other decorative uses. All parts of the plant can be used for tanning. The concentrations of tannin vary from 17% in the leaves to 9% in the bark and 7% in the fruits. Siamese senna is used in China as a host plant for the lac insect. In India, it is used as a host for sandalwood (Santalum spp.), a parasitic tree producing the well-known aromatic (Orwa et al., 2009).

Senna siamea provides many environmental services. It is used to reforest denuded hills and mining sites, for shade and hedges, as windbreaks, and it is planted as an ornamental (Ecocrop, 2019). Siamese senna has been mentioned as a potential agroforestry species (Ecocrop, 2019).


The origin of Senna siamea is debated. It has been thought to originate from Asia in a range between 25°N and 5°S including southern India, Sri Lanka, Myanmar, China, Thailand, Cambodia, Malaysia, and parts of Indonesia. However, its native range may be more restricted (Rojas-Sandoval et al., 2013; Orwa et al., 2009). Siamese senna was widely introduced in central and northern India, in tropical Africa, in the Americas and in the Pacific, originally as an avenue shade tree for roadside planting. It has been used in afforestation and soil reclamation projects (Rojas-Sandoval et al., 2013). It has become naturalized in many places and has been reported as invasive in several countries (Rojas-Sandoval et al., 2013).

Senna siamea can be found from sea level up to an altitude of 1400 m, but it is generally a lowland species. It is particularly suited to lowland tropics with a monsoon climate though it does well where annual temperatures range between 20 and 31° C, and where annual rainfall is between 400-2800 mm with a dry season not exceeding 4-8 months. Siamese senna does not withstand cold (< 10°C) and is killed by frost. For these reasons Senna siamea grows better below 1300 m altitude. It is a full sunlight species. Senna siamea does better on deep, well-drained fertile soils with pH 5.5-7.5, but can grow on degraded lateritic soils provided drainage is not impeded. The species is intolerant of saline soils (Orwa et al., 2009).

Forage management 


Siamese senna can be sown directly or in containers and then planted. It should be sown in line to a depth of 4-5 cm. After germination, the seedlings should be thinned to a spacing of 30 cm at the end of the first rain and then to 1.8 m x 1.8 m in the following rainy season. Siamese senna grows very fast: in India, a height increment of 2.5 m per year has been recorded. In West Bengal, 3-year old trees were almost 8 m tall with a stem girth of 25 cm (Rojas-Sandoval et al., 2013). Siamese senna can be cut a 1 m height every 6 month to provide maximum foliage (Akkasaeng et al., 1989)


In Thailand, Senna siamea provided one of the highest yields of edible material out of 14 forage trees, with an accumulated dry matter production of 2.7 kg per tree (Akkasaeng et al., 1989).

Environmental impact 

Afforestation and soil reclamation

In India, Senna siamea is planted in degraded and dry areas for rehabilitation of forests, and it holds promise for reclamation of mined areas (aluminium mine tailings)(Orwa et al., 2009). It has been used in a afforestation program aiming at fixing the fly ash from a thermal power station in India (Lal, 1996). In Northern Ghana, where the disappearance of tropical forest is alarming, Siamese senna had higher growth rate than the neem tree (Azadirachta indica) and was recommended for afforestation (Damian et al., 2014).

Erosion control and soil improver

Siamese senna planted in hedgerows increased topsoil infiltration, reduced runoff and prevented soil erosion. A well-grown tree can yield 500 kg/year of fresh leaves that can be used as green manure. Senna siamea forms ecto-mycorrhizae and provides very useful mulch, especially in alley-cropping systems (Orwa et al., 2009).

Boundary or barrier or support, shade and shelter

Siamese senna trees planted in hedgerows provide live fence around food crops. It can be grown as a shade tree along roads and in cocoa, coffee and tea plantations. It is a useful windbreak and shelterbelt (Orwa et al., 2009).


Due to its fast growth and prolific seed production, Senna siamea is considered to be invasive in Australia (especially the Cape York Peninsula, Queensland), Mexico, the Caribbean (Dominican Republic and Puerto Rico), the Pacific (Fiji and French Polynesia) and Africa, and may pose a significant risk of invasion in other countries where it is already present and cultivated (CABI, 2018).

Nutritional aspects
Nutritional attributes 

Senna siamea is a legume tree and its foliage is thus relatively rich in protein (about 13-20% DM), though in lower amounts than that in other tropical legume trees such as Leucaena or Gliricidia.

The seed is rich in protein (25% DM) with a relatively low lysine content (3.6% of the protein), but information is limited (Ingweye et al., 2010).

Potential constraints 

Toxic and antinutritional factors

The leaves and seeds of Siamese senna contain anthraquinones, alkaloids, phylobatannins, saponins, tannins (though not condensed tannins), oxalates and phytate (Alli Smith, 2009; Jackson et al., 1996; Ingweye et al., 2010). All those sustances are potentially deleterious or toxic to monogastric livestock and to humans, and the foliage or the seeds may require processing before consumption.


Even though the plant is widely available as fodder in many tropical regions, particularly iThere are very few studies on the use of Senna siamea foliage for ruminants.

Palatability and intake

The few studies available report a low palatability and intake compared to other forage trees. In Nigeria, Senna siamea foliage tested in a cafeteria experiment where it was compared to 7 other legume trees was totally rejected by sheep, probably due to the hard physical structure of the leaves (Fadiyimu et al., 2011). In the Philippines, leaves offered to goats were less consumed than those of other trees or shrubs. This low intake may be due to the low pH value (3.73) measured in the leaves (Aban et al., 2015).

In Ghana, Senna siamea leaves offered as supplement for 3 hours/d to one year Djallonke lambs (12.6 kg) grazing natural rangeland resulted in a low DMI (12 g DM) compared to leaves of other legume trees (106 to 263 g DM), but average daily weight gain was comparable (35 vs 33-55 g/d) and higher than without supplementation (12.7 g/d). When the leaves were included at 40% into a total mixed ration including rice straw (58%) and minerals (2%), total DMI of rams (14 kg) was significantly lower (255 g DM/h/day) compared to other trees (456 to 509 g DM/h/d) but the DM digestibility was not different (57 %) although trending lower than other leaves (59 to 69%) (Ansah et al., 2016)

Digestibility and degradability

In Thailand, Senna siamea leaves offered as supplement with rice straw to swamp buffaloes allowed a similar fibre digestion to that obtained with Leucaena leucocephala and Morus alba (Jetana et al., 2013). In Nigeria, Senna siamea leaves were in the top group for DM degradability (> 70%) when compared to 24 other legume tree forages offered to cattle, sheep or goats (Larbi et al., 1997).


No information could be found (2019). All parts of Senna siamea contain compounds toxic to monogastric animals, so it should not be recommended for pigs until trials demonstrate its safety.


No information could be found (2019). All parts of Senna siamea contain compounds toxic to monogastric animals, so it should not be recommended for poultry until trials demonstrate its safety.



Information in the international literature on the use of Senna siamea leaves as forage for rabbits is very scarce and limited to two experiments in Nigeria (as of 2019). When offered to growing rabbits, fresh leaves of Siamese senna were consumed in noticeable quantities and apparently safely in spite of the presence of antinutritional compounds (Ocheja et al., 2011; Yusuf, 2019).

In one experiment, fresh senna leaves distributed together with a balanced concentrate ad libitum were able to provide a growth rate identical to that of the all-concentrate diet used as control. Using senna leaves saved 22% of the concentrate and represented 42% of the total DM intake. Better growth results (23% growth rate increase above control) were obtained with Tridax procumbens, but the protein content of tridax was 16.3% DM while it was only 7.6% DM for the senna leaves, a value that is abnormally low (Yusuf, 2019).

In an another experiment, the daily distribution to rabbits (only 4 per treatement) of a fixed quantity of forage (100 g/head) in addition to a fixed quantity of unbalanced concentrate (Bambara nut waste + rice offal 3:1, 50 g/head) resulted in growth performance similar for Senna, Gmelina or teak leaves (8-10 g/day) while growth was better (12 g/d) with bamboo leaves (Ocheja et al., 2011). Though this growth performance reflects the nutritional balance of the final ration (forage + concentrate) rather than true relative value of each forage, this experiment still demonstrates that each forage, including Senna siamea, was readily consumed by rabbits.


Siamese senna seeds are rich in protein and could thus be valuable for rabbit feeding, but direct experiments with rabbits are necessary before these seeds can be recommended.

Nutritional tables
Tables of chemical composition and nutritional value 

Avg: average or predicted value; SD: standard deviation; Min: minimum value; Max: maximum value; Nb: number of values (samples) used

Main analysis Unit Avg SD Min Max Nb  
Dry matter % as fed 38.4 4.7 33.9 44.8 5  
Crude protein % DM 17.2 3.1 12.4 21.6 17  
Crude fibre % DM 20.1 4.1 16.4 25.5 6  
Ether extract % DM 6.9   4.3 11.2 4  
Ash % DM 7.7 2.2 5.2 11.2 10  
Neutral detergent fibre % DM 44.7 6 33.8 53.5 8  
Acid detergent fibre % DM 28   25.7 29.8 4  
Lignin % DM 11.4       1  
Gross energy MJ/kg DM 19.4         *
Minerals Unit Avg SD Min Max Nb  
Calcium g/kg DM 10.2   5.7 16.3 4  
Phosphorus g/kg DM 1.6 0.2 1.4 1.9 5  
Magnesium g/kg DM 2.4   2 3.1 4  
Potassium g/kg DM 7.2   3.9 11.2 3  
Sodium g/kg DM 0.62   0.06 1.6 3  
Sulfur g/kg DM 1.9   1.8 1.9 2  
Manganese mg/kg DM 220   23 417 2  
Zinc mg/kg DM 33   12 55 2  
Copper mg/kg DM 4   3 6 2  
Iron mg/kg DM 255       1  
Secondary metabolites Unit Avg SD Min Max Nb  
Tannins (eq. tannic acid) g/kg DM 10       1  
Tanins, condensed (eq. catechin) g/kg DM 1   0.8 2 2  
In vitro digestibility and solubility Unit Avg SD Min Max Nb  
In vitro DM digestibility (pepsin-cellulase) % 64   62 66 2  
Ruminant nutritive values Unit Avg SD Min Max Nb  
DE ruminants MJ/kg DM 13.4         *
ME ruminants MJ/kg DM 10.8         *
Energy digestibility, ruminants % 68.7         *
OM digestibility, ruminants % 71.9         *
Nitrogen degradability (effective, k=6%) % 66   58 74 2 *
Nitrogen degradability (effective, k=4%) % 72         *
a (N) % 37   21 52 2  
b (N) % 55   40 70 2  
c (N) h-1 0.07   0.067 0.073 2  
Dry matter degradability (effective, k=6%) % 61   54 68 2 *
Dry matter degradability (effective, k=4%) % 65         *
a (DM) % 40   27 53 2  
b (DM) % 39   29 50 2  
c (DM) h-1 0.068   0.067 0.069 2  
Rabbit nutritive values Unit Avg SD Min Max Nb  
DE rabbit MJ/kg DM 10.5         *
MEn rabbit MJ/kg DM 10         *
Energy digestibility, rabbit % 54.1         *
Nitrogen digestibility, rabbit % 54.7         *

The asterisk * indicates that the average value was obtained by an equation.


Aban et al., 2015; Akkasaeng et al., 1989; Ansah et al., 2016; Bhannasiri, 1970; Blair et al., 1988; CIRAD, 1991; Fadiyimu et al., 2011; Jackson et al., 1996; Larbi et al., 1997; Larbi et al., 1998; Lim Han Kuo, 1967; Mtui et al., 2008; Oduguwa et al., 1997; Pozy et al., 1996

Last updated on 07/08/2019 15:40:54

Datasheet citation 

Heuzé V., Tran G., Hassoun P., Lebas F., 2019. Siamese senna (Senna siamea). Feedipedia, a programme by INRA, CIRAD, AFZ and FAO. https://www.feedipedia.org/node/323 Last updated on August 7, 2019, 23:13