Alternative Name(s):
Coffee senna (Senna occidentalis) Weed.
Arsenic Bush.
Family:
Fabaceae (Caesalpinioideae).
Form:
Shrub.
Origin:
Native of America.
Flowers/Seedhead:
In racemes of 2–6 flowers in upper leaf axils or terminal. Flowers with sepals shorter than petals, petals 0.8–1.5 cm long, bright yellow. Flowers summer to winter.
Description:
Annual to short-lived perennial shrub to 1.2 (rarely to 2) m high. Stems almost hairless when mature. Stipules falling early. Leaves with leaf axis and leaf stalk 4–18.5 cm long (leaf stalk 1.5–6 cm long), leaflets lanceolate to ovate, hairless except for scattered to common hairs on margins. Seedpod hairless, straight or sickle-shaped, opening at maturity, with seeds transverse in seedpods. Seeds ovate to oblong, flattened, olive to dark brown, 0.4–0.5 cm long.
Distribution Map:
Coffee senna (Senna occidentalis) Distribution in North America shown in green.
Distinguishing features:
Close up of Coffee senna (Senna occidentalis) Weed.
Distinguished by foetid odour; absence of spines and prickles; leaves with 3–7 pairs of leaflets that are 2–10 cm long, 0.6–4 cm wide, mounded gland at base of leaf stalk, no glands between leaflets; inflorescence stalk 0.2–0.5 cm long; flowers with 10 stamens and sterile stamens, 6 or 7 fertile anthers; seedpod cylindrical, 7.5–12.5 cm long, 0.8–1.1 cm wide, seeds numerous (20–50).
Dispersal:
Spread by movement of seed.
Confused With:
Other Senna species.
Notes:
Seeds have been used as a coffee substitute. Can be a serious competitor with crops and pastures and may be toxic to stock, although rarely eaten. Now a pantropical weed.
