What is a Fever Tree

The fever tree is an African thorn tree of the genus Acacia.

Acacias occur naturally everywhere except in Europe and Antarctica, but are most prevalent in Australia (729 species – most well known is the wattle) and Africa (115 species). The scientific name of the fever tree is A. xanthophloea. European pioneer farmers in Africa believed that the trees somehow contributed to fever, hence the origin of the common name. It is currently accepted that the only connection is that they occur in areas where malarial mosquitoes breed, i.e. in and near water and especially in swampy areas. Malaria is characterised by bouts of intense fever.

Fever trees usually occur in a woodlands aspect, from Somalia in North Africa to the Republic of South Africa, and are easily recognised by their bark, which is smooth, slightly flaking, and greenish-yellow to yellow. In the wild the bark is stripped by elephants. The leaves are compound and appear feathery. The sweetly scented yellow (white in some areas) flowers are borne in spherical heads from August to November. The pods are light brown, small, straight, papery thin, with slight constrictions between the seeds and is a favourite food for vervet monkeys. The thorns are long, straight and paired. It has a slender to spreading, sparse, roundish crown. (Many African species of Acacia characteristically have flat tops whereas most Australian species tend to develop spherical crowns.) The trees vary widely in height, dependent on water stress, but is generally about 15 to 25 m high. It is deciduous (loses its leaves seasonally).

Like all Acacias, the fever tree is a nitrogen fixer through the activity of microbes associated with it’s roots. Leaf fall beneath the canopy also contributes to its enriching effect on the soil.

The fever tree is one of the most widely cultivated of the indigenous African thorn trees. It is a fast grower (1 – 1.5 m per year), and a favourite for birds to nest in. It’s shade is sparse therefore other plants can grow beneath it. It is sensitive to frost and temperatures below 25 degrees F. It can be propagated from seed that has been soaked overnight in boiling water and prefers to be planted in loamy soil.

In South Africa the Zulu witchdoctors use fever tree bark concoctions to enter a prophetic dream state in which they can receive messages from the ancestors. Leaves are also steeped to make a tea for treating coughs and bronchitis.

Taxonomical note: In Australia the genus has been placed in the family Mimosaceae by Jacobs and Pickard (1981) and in the family Leguminosae (sub-family Mimosoidae) by Green (1981). In Africa the family name Fabaceae is preferred (Ross 1979). There are three subgenera: Acacia, Aculeiferum, and Heterophyllum. There is also a tree called the forest fever tree, which is Anthocleista grandiflora, a straight-stemmed evergreen with very large leaves, that occurs in eastern and southern Africa and the Comores.