Gigasiphon macrosiphon is a medium-sized tree, one of three species in the genus Gigasiphon (family Fabiaceae, or legumes). A species potentially interesting to ornamental horticulturalists, it has large attractive white flowers striped with yellow and the tree grows to about 20 meters. The seeds are hard, smooth and button-shaped, with a light stripe around the perimeter. G. macrosiphon grows in moist lowland and coastal forests in Kenya and Tanzania. Continual destruction of East African coastal forests and use of this plant for firewood, tools, charcoal and lumber, has reduced the G. macrosiphon population to 33 known mature individuals in the wild. These are found in Kaya Muhaka, Gongoni, Marenje and Mrima Forest Reserves (Kenya) and Amani Nature Reserve, West Kilombero Scarp Forest Reserve, Kihansi Gorge and Rondo plateau (Tanzania). The IUCN assessed G. macrosiphon with endangered status in 1997 and in a report in conjunction with the Zoological Society of London (ZSL) placed this species on their list of 100 most endangered species in 2012.
(Baillie and Butcher 2012; CAMP Workshop 1998; Lovett et al. 2006; J.Robertson 1998; Verdcourt 1982)