The City Park Botanic Gardens plays an important function as a safe haven, for endemic plant species from the wider region that have become threatened in their natural habitats.
Examples of other endangered native plants that have been introduced into the Park include Aloe ballyi, the tall-growing ‘Tree Aloe’ that is endemic to the Voi–Taita region of Kenya, and the Cycad, Encephalartos hildebrandtii, which is native to coastal forests in East Africa.
Two species of Palm, including the massive ‘Borassus Palm’, Borassus aethiopum (Mvumo in Kiswahili), from the coastal region, have also been planted in the Park’s botanic garden.
In all, no fewer than 110 of the plants in Botanic Gardens are classed as being of high conservation priority. Sixteen of these are endemic species (including seven that, in the wild, occur only in Kenya, and nine that, as regional endemics, are found only in East Africa).
Of the 560 plant species that are known to occur in City Park, representing some 390 genera in more than 120 families, only about one-quarter (that is, about 140 species) are exotics that originate in countries outside Africa.
Most of these exotic trees – such as the familiar Grevillea (G. robusta) and ‘Blue Gum’ (Eucalyptus spp.) from Australia, as well as the Jacaranda (J. mimosifolia) and Bombax (Chorisia speciosa), both from Brazil – probably introduced themselves, courtesy of seeds blown in from nearby city lots and gardens, where these trees are widely cultivated, either as ornamentals or for firewood.
Birds have doubtless been responsible for introducing some of the exotic fruit trees, mainly Guavas (Psidium guajava), from private gardens in the neighbourbood.
Some exotics, such as the Bougainvillea (B. spectabilis), native to Brazil, the pink-flowering ‘Norfolk Island Hibiscus’ or ‘Pyramid Tree’,Lagunaria patersonii, from Australasia, and the magenta-pink- or white-flowering ‘Camel’s Foot’ (both varieties of Bauhinia variegata), native to Asia, have been planted around Park buildings to lend a splash of colour.
Other colourful exotics, such as the spectacular, red-flowering ‘Flamboyant’ (Delonix regia), from Madagascar, and the ‘Persian Lilac’ or ‘Chinaberry’ (Melia azedarach), have been planted on the Park lawns, again for purely ornamental reasons. There is, in City Park, even a sapling Gingko biloba, a species revered in its native China.
A Jacaranda growing near the Bandstand, a Botanic Gardens central feature, whose flowers are snow-white, rather than the usual mauve-blue, is another talking point among the Park’s attractions.
Wildflowers on view in the Botanic Gardens at various times of the year include, most spectacularly, those of the tendril-leaved ‘Flame Lily’, Gloriosa superba, a brilliant red streaked with yellow, appearing after the rains. The bristly pink-red flower heads of the ‘Fireball Lily’, Scadoxus multiflorus, fond of shaded ground, can also be very eye-catching. Found growing in profuse clusters near the river and along its feeder-streams is Acanthus pubescens, a low shrub with dark green, heart-shaped leaves and attractive purple-blue flowers.
Representing the ‘Morning Glory’ family (Convolvulaceae) are several Ipomoea creepers, including the palemauve-flowering I. cairica and the magentapink- blooming I. wightii, a regional endemic. Clearings may be carpeted with ‘Black-eyed Susan’, Thunbergia alata, flowers: orange with dark purple centres (providing targets for would-be pollinators). Thunbergia holstii, a shrub whose trumpet-shaped, bluish-purple flowers have yellow centres, is also present, as is Commelina benghalensis, a low herb that after rain produces delicate bright blue flowers, and Aneilema aequinoctiale, producing brilliant yellow flowers. A Pentas, P. lanceolata, with pale mauve-pink flowers (as opposed to the brilliant red of the more familiar parvifolia) grows in City Park, along with an upland form of the trailing herb Justicia diclipteroides, with magenta-coloured flowers, and Lagenaria abyssinica, from the Cucumber family (Cucurbitaceae), with green-veined white flowers that open in the evening. All are typical wildflowers of the dry upland forests around Nairobi.
City Park’s well-developed Plant Nursery, meanwhile, continues to nurture saplings, grown from seeds and wildlings collected in the Park, for onward dissemination to other nurseries, both in the Nairobi area and further afield. This underlines another of the Park’s key functions: that of bolstering the wider conservation effort.