Sword bean (Canavalia gladiata) belongs with jack bean (Canavalia ensiformis) to the Canavalia genus, a neglected group of legumes that has however many valuable characteristics. A tropical perennial legume, it is mainly cultivated as an annual (Ekanayake et al., 2000).
Morphological description
Sword is a perennail legume mainly cultivated as an annual (Ekanayake et al., 2000)/ Sword bean has a vigorous climbing or trailing habit and can be up to 10 m long. Some cultivarrs may also be semi-erect. Sword bean root system is deep. Its stems are woody . The leaves are alternate, large, trifoliolate. Sword bean leaflets are oval-shaped, 7.5–20 cm long × 5–14 cm broad, shortly pubescent on both faces. The inflorescence is a large axillary raceme (7 to 12 cm long) bearing several flowers. The flowers are papillonaceous, inverted, white to pink in colour. The fruits are long (20-40 (-60) cm, straight, rough-surfaced and slightly compressed dehiscent pods containing 8 to 16 seeds. The seed are 2-3.5 cm -1.5-2 cm, oblong-ellipsoid in shape, very variable in colour. They range from red, red-brown to white or black. The hilum is as long as the seed, dark brown in colour (Bosch, 2004; Duke, 1981)
Uses
Though a neglected crops at international level, sword bean may be of utmost importance in some places (Ekanayake et al., 2000). Its forage and seeds have many nutritional and ethnomedicinal properties. Sword bean seeds and pods are edible and nutritious they are used for culinary purpose and can replace broadbeans in many recipes. They are used to make soups, stews in many countries of Asia (Sri Lanka, India, Indonesia, China, Korea and Japan), in Madagascar (Bosch, 2004). In Tanzania the swahili expression for "eating sword bean" means "being happy" (Bosch, 2004).
When the mature seeds are used for cooking, because of anti-nutritional substance, they must be first dehulled, then carefully soaked in salted water, sometimes fermented and finally cooked. It was recommend to make a test before eating large quantities of sword bean seeds (Duke, 1981).
Sword bean may also be used as fodder and cover crop. The seeds may be fed to cattle and chicken provided it is moderately consumed (see Potential constraints").Sword bean foliage is a useful forage for ruminants (Graham et al., 2003 cited in Dada et al., 2013).
In some places, sword bean is used as an ornamental climber on fences and houses. It is also used as a cover crop. It is believed to repel snakes.
Sword bean has many ethnomedicinal properties and it is a source of urease, a useful compound for urea blood analysis in humans (Bosch, 2004)
Canavalia species ranks well among the neglected crop species (Dada et al., 2012; Ekanayake et al., 2000). The nutritional, pharmaceutical usefulness of this legume both to man and his livestock are outstanding; the seeds are used as food for man while foliage is important as meal for animals (Graham and Vance, 2003). The immature pod of most legumes is rich in protein, minerals and vitamins while the seeds are the most nutritious part (Nwokolo, 1987). The fruits of Canavalia spp. have been reported as potential sources of nutritional (Ekanayake et al., 2000), nutraceutical, (Nwokolo, 1987) and pharmaceutical benefits for humans and livestock, (Grubben and Denton, 2004). Both species of Sword bean (Canavalia gladiata) Jack bean (Canavalia ensiformis) are used in Nigeria as ornamental plants and in some places are believed to be “snake repellents”. Sword bean contains gibberellin A-15, a growth-promoting hormone (Tokoya and Takama, 1981)
In Madagascar the young green fruits and immature seeds of sword bean are used as a cooked vegetable (Bosch, 2004). Sword bean is eaten in Tanzania, where the Swahili expression ‘eating sword bean’ means ‘being happy’ (Bosch, 2004). Use of the fruits and immature seeds is also reported from Sri Lanka, India, Indonesia, China, Korea and Japan (Bosch, 2004). Sword bean is further planted as a forage and cover crop (Bosch, 2004). The ripe seeds can be eaten after cooking, but only after removing the seed-coat and several changes of water (Bosch, 2004). The seed is used as feed for cattle and chicken, but if eaten in considerable quantity dry seeds may cause poisoning (Bosch, 2004). Sword bean is grown as an ornamental climber on fences and houses.
