Nearly two-thirds of the Nairobi Arboretum is covered by a greenery dry forest vegetation, with an impressive collection of more than 350 species of mature trees, from all over the world, including the tropics. Other plants life in the Arboretum are shrubs, grasses, climbers, herbs, orchids, mosses and fungi, which have not been explored fully hence, much remains to be discovered.
The Arboretum is not only about plants; it also hosts a variety of wildlife, including small mammals, reptiles, insects and an impressive array of bird species. There are over 100 species of migrant and resident bird species, with some of the rare forest-dependent birds recorded. The mammals include two species of monkeys, the vervet (Cercopithecus aethiops) and the Sykes’ monkey (Cercopithecus mitis), small burrowing rodent, the Kenya mole rat (Tachyoryctes ibeanus) and four-toed hedgehog (Erinaceus albiventris). Others like the greater galago, fruit bats, mongooses and squirrels, may also be seen in the arboretum. These are mostly nocturnal animals unlikely to be seen during the day.
The arboretum is particularly rich in insects especially the butterflies, from the harder to see forest-dwelling species, to those living in open, sunny areas exhibiting a variety of colours. The arboretum also is home to various reptiles, including Jackson’s three-horned chameleon and high-casqued chameleon. Snakes have been sighted but are very rare.
This array of lush greenery or “natural environment” has made the arboretum a popular destination for nature lovers.