Common Name: Devil Bean

General Information

Crotalaria retusa is an erect, annual plant or short-lived perennial with more or less woody stems. It can grow from 60 - 120cm tall[].
The plant is harvested from the wild for local use as a food, medicine and source of materials. It is sometimes cultivated for the fibre it provides, as a medicinal plant, and is also grown as a green manure crop[, ]. It is occasionally grown purely as an ornamental, though it is also sometimes considered to be a weed[].

Known Hazards

The plant is reported to yield toxins, such as the pyrrolizidine alkaloid monocrotaline, and is said to have poisoned poultry and livestock in Nigeria[].
Many members of this genus are known to contain pyrrolizidine alkaloids, the most potent of which in this genus are monocrotaline, retrorsine and retronecine[]. These alkaloids have a cumulative effect upon the body and, unless concentrations in a plant are high, occasional consumption is generally completely safe. Pyrrolizidine alkaloids are derived from amino acids including ornithine. Many of these alkaloids have pronounced hepatic toxicity, but the lungs and other organs may be affected as well. Mutagenic and carcinogenic activities of pyrrolizidine alkaloids have also been reported[].

Botanical References

,

Range

Pantropical.

Habitat

Coastal grassland, along rivers, waste places and fields, at elevations up to 250 metres[]. Open places in deciduous dipterocarp forests; at elevations up to 1,500 metres[].

Properties

Weed Potential	Yes
Edibility Rating
Medicinal Rating
Other Uses Rating
Habit	Annual
Height	1.20 m
Cultivation Status	Cultivated, Ornamental, Wild

Cultivation Details

Plants in this genus generally prefer a sunny position, succeeding in dry to moist, well-drained soils[].
Grown as a green manure, fibre crop and ornamental, the plant has escaped from cultivation and become naturalized in some areas. It is considered to be invasive in some areas - in Hawaii, for example, it is naturalized in disturbed sites such as roadsides, dump sites and urban areas[].
The plant can flower and produce fruit all year round[].
This species has a symbiotic relationship with certain soil bacteria, these bacteria form nodules on the roots and fix atmospheric nitrogen. Some of this nitrogen is utilized by the growing plant but some can also be used by other plants growing nearby[, ].

Edible Uses

The flowers and leaves have a sweet flavour and are edible as a vegetable[, ]. Their alkaloid content is very low[].

The roasted dehulled seeds are eaten in Vietnam[]. The seedpods contain about 10 - 20 yellow-brown to blackish heart-shaped seeds measuring about 5 mm x 3 mm[]. Some caution is advised, see notes on toxicity[].

Medicinal

The roots are used against coughing up blood[].

The plant is used as a treatment for complaints such as cough, dyspepsia, fever, cardiac disorders, stomatitis, diarrhoea, scabies and impetigo[].
An infusion of the plant is used to bathe children in order to prevent skin infections and also to treat thrush[].

The leaves, mixed with those of Crotalaria quinquefolia, act internally as well as externally against fever, scabies, lung diseases and impetigo[].

A decoction of the flowers and leaves is used to soothe a cold[].

The seeds are eaten raw to act as an analgesic to deaden the pain of a scorpion sting[]. The powdered seeds, mixed with milk, are eaten in order to increase body strength; they are also used to treat skin diseases[].

The plant contains hepatotoxic pyrrolizidine alkaloids[].

Agroforestry Uses:

Crotalaria retusa is grown as a green manure and as a cover plant in plantations of coffee, oil palm etc[, ]. It is an excellent source of organic matter - its fresh foliage usually contains between 0.5 - 1% nitrogen, which when incorporated into the soil improves fertility and nutrient retention, while providing structure to the soil by enriching it of humus and retarding erosion[].
Like many other members of the genus, the plant is nematode-resistant[]. It is grown as a green manure in order to reduce nematode infection in the soil - the growing plant encourages nematodes to hatch, these are then unable to feed on the Crotalaria and so many of them die.

Other Uses

A strong fibre is obtained from the bark and stems[, ]. It is used for cordage and making canvas[].

Used as a dye plant in East Africa[].

A non-edible, non-drying oil of low unsaturtion is obtained from the seed. It has a potential for use in the production of hair shampoos, skin cream and shoe polish[].

Propagation

Seed - sow in situ. Pre-soaking the seed for 12 hours in warm water can help to reduce germination time.

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