The length increments of seedlings and branches, and the extension growth of specimens of different age classes of 12 forest tree species were measured on Mt Kenya between May 1992 and July 1995.

Of all examined species, the camphor tree, Ocotea usambarensis showed the lowest growth rates. The growth rates of other species of the primary forests, namely Zanthoxyllum gillettii and Vitex keniensis were between 30 and 200 % higher. The seedlings of Vitex outgrew even pioneer species such as Macaranga kilimandscharica Pax and Neoboutonia macrocalyx. These trees showed growth rates at least twice as high as those of the primary species.

Juniperus procera was found to be the fastest growing species in the cedar forest, underlining its success in forming dense stands after a fire. Only young Podocarpus latifolius showed a similar fast growth. Olea europaea ssp. cuspidata, Olea capensis ssp. hochstetteri and Cassipourea malosana had nearly equal growth rates, however, considerably lower than those of Juniperus procera and Podocarpus latifolius.

Hagenia abyssinica fell within the range of the fast growing species, illustrating the ability of this species to regenerate very fast under suitable conditions.