At higher altitudes (over 1 500 m), in the south-west, the Teita Hills are covered by an evergreen forest with the camphor tree (Ocotea usumbarensis), the predominant species. Mt. Kasiagu has a small area of forest with Newtonia buchanani predominant between 1 300 and 1 600 m.
Evergreen or semi-deciduous upland forests
The upland forest belt in the wetter zones begins with the plateau forests, between 1 300 and 2 000 m. They occur in the central part of the country (in the neighbourhood of Nairobi, Ngong, Kiambo and Nyeri) in areas with an annual rainfall of 850 to 1 000 mm and a cool, equatorial climate. These forests are evergreen or semi-deciduous. Brachylaena hutchinsii (muhugu) and Croton megalocarpus dominate the evergreen type. The semi-deciduous type is less rich in species.
The largest areas of upland forest occur on the main mountains between 2 000 m to about 3 500 m on Mt. Kenya, Mt. Elgon, the Aberdare range, the Laikipia escarpment and the Mau-Elgeyo-Cherangani mountain system. This evergreen forest can be subdivided into the following types:
- Forests dominated by Ocotea spp. The most important species is O. usambarensis (east African camphor tree), a large tree up to 45 m high, often associated with Myrica salicifolia. These forests occur on very dissected terrain. The lower parts of the valleys and ravines may contain Syzygium spp., Ilex mitis, Ficalhoa laurifolia, Ensete vertricosum and tree ferns. The Ocotea forests present regeneration problems, as the seeds are threatened by predators and the suckers by elephants; forest occurs in the wet montane zone within the elevation range of 1 500 to 2 400 m. Aningeria is associated with Albizia spp., Alangium chinense, Allophylus abyssinicus, Casearia battiscombei, Tabernaemontana spp., Croton macrostachys, Syzygium guineense and others.
- The Aningeria adolfi friederici
Pilar wood (Cassipourea malosana) forest occurs on the south-west and north-east slopes of Mt. Kenya and in the north-eastern Aberdares. Tree species in the canopy (9 to 21 m) also include Albizia gummifera, A. schimperania, Fagara spp. Hagenia spp., Ilex mitis, Macaranga kilimandscharica, M. conglomerata, Ocotea usambarensis, Prunus africana, and Rapanea rhododendroides.
Only small remnants are left of coastal forests on the wetter soils of the hills and along the rivers. Below 350 m, on sites with more moisture, a mixed evergreen forest occurs with an abundance of Afzelia and Trachylobium species.
Mangroves are scattered along the coastal belt in the inter-tidal zones on estuaries and along creeks. Nikoko, (Rhizophora mucronata) and mkandaa (Ceriops tagal) grow together with other species.
Bamboo and palms
In the intermediate and wetter zone of the uplands, between 1 800 and 3 300 m, the mountain bamboo (Arundinaria alpina) covers large stretches on the Mau and the Aberdare Ranges. It also occurs in scattered patches on the eastern side of Mt. Elgon. In the bamboo thickets, shrubs such as Mimulopsis spp. can be found.
Patches of a forest type dominated by Ocotea usumbarensis and Podocarpus spp (mainly P. milanjianus) often occur in the belt between 1 700 and 2 400 m above sea level with a rainfall of about 2 200 mm on the eastern slopes of the Alberdares and Mt. Kenya. Juniperus forest is widely distributed in the drier highland areas, ranging from 1 000 to 2 900 (with major development betwen 1 800 and 2 900 m) and an annual rainfall of around 1 100 mm. Olea africana, Podocarpus gracilior, P. milanjianus and Croton megalocarpus may accompany Juniperus.
Excessive populations of big game damage these forests on the hills and mountain in northern Kenya. On the eastern side of Mt. Elgon, around 2 800 m, Podocarpus trees are widely spaced and growing up to 30 m, with a few trees of Olea hochstetteri growing up to 20 m in between. Many smaller hardwood trees are also present. In the intermediate and wetter zone of the uplands, between 1 800 and 3 300 m, the mountain bamboo (Arundinaria alpina) covers large stretches on the Mau and the Aberdare Ranges. It also occurs in scattered patches on the eastern side of Mt. Elgon. In the bamboo thickets, shrubs such as Mimulopsis spp. can be found.