Tree to 18 m, ≥ 1 m dbh. Crown rounded to umbrella-shaped. Bark reddish brown to brown, ridged, flaky. Branches massive, wide-spreading. Branchlets densely covered with golden hairs, leaf scars prominent. Leaves imparipinnate, to 40 cm long with five to seven (to eight) pairs of major leaflets, alternating with one (to three) very small, subcircular leaflets; rachis covered with soft, drooping hairs; major leaflets narrowly oblong, 12–15 × 3.5–5.5 cm, upper surface largely glabrous, viscid, lower surface covered in silky hairs, margins finely dentate, apex acuminate; petiole to 15 cm long, with hairs as on rachis; stipules (3–)6–9 cm long, membranous, reddish to brown, almost entirely fused to the petiole. Inflorescences paniculate, terminal, drooping, to 60 cm long with numerous flowers; male and female flowers typically on separate plants. Male flowers white to orange, ~0.8 cm diameter; female (and hermaphrodite) flowers red, viscid, to 1.5 cm diameter; epicalyx present, sepals (four to) five, petals (four to) five, stamens up to 20. Fruit an achene, enclosed within the calyx tube. Graham 1960, Mendes 1978. Distribution BURUNDI; DEM. REP. CONGO; ETHIOPIA; KENYA; MALAWI; RWANDA; SUDAN; TANZANIA; UGANDA; ZAMBIA. Habitat Montane rain forest, deciduous woodland and evergreen bushland between 1950 and 3000 m asl. USDA Hardiness Zone 9–10. Conservation status Not evaluated. Illustration Graham 1960; NT383.
Hagenia abyssinica is one of the iconic trees of the Afromontane forests of East Africa, always looming somewhere in the misty background of any documentary on Mountain Gorillas. With its massive trunk and wide-spreading limbs, big pinnate leaves and pendulous reddish inflorescences, it is immediately recognisable. In its native forests it requires an open site for germination and establishment, often regenerating following a disturbance event such as a landslide or fire, and is only found in the cooler, misty upper parts of the forest (Grimshaw 1996). Here the nocturnal temperatures drop to close to freezing point most nights of the year, but at ground level a frost would be exceptional. Establishment outside the forest is rare and such seedlings are regularly frozen and damaged. As a consequence H. abyssinica, while a highly desirable tree, is unlikely to become frequent in our area, where few regions are cool enough and yet sufficiently frost-free for it to be successful. Woodland gardens with a high canopy in the Celtic extremities of western Europe would be ideal, and it is grown in just such conditions at Tregrehan, where a young plant is doing well and is now 1.5 m tall after two seasons in the ground (T. Hudson, pers. comm. 2007). Another area where it should flourish is the California coastal mist belt, centred on San Francisco, but there is no evidence of its being cultivated there. It is, however, grown in New Zealand (T. Hudson, pers. comm. 2007). In areas where it grows wild local populations value it for its medicinal properties – a ‘popular and highly effective anthelmintic’, according to the Flora of Tropical East Africa (Graham 1960).