William Keit (originally Julius Wilhelm Keit), a German gardener from Dresden, moved across Europe as a young man, working in gardens and nurseries in Munich, Basle, Brussels, Dublin, and Nottingham. In June 1868 he joined the staff of the Royal Botanic Gardens of Ireland at Glasnevin, a small town just north of Dublin, under the direction of Dr David Moore. In September 1869 he accompanied Moore's two children to a boarding school in Hanover. By 1872 he was foreman of the propagating houses at Glasnevin and according to Moore was "an excellent practical gardener and very ingenious at applying various methods for propagating plants" (McCracken, 1986, p. 72). That year the Natal Agricultural and Horticultural Society appointed him, on the recommendation of Dr Moore and Sir Joseph Hooker*, as curator of the Natal Botanic Gardens, Durban, succeeding M.J. McKen*. He arrived in Durban on 14 December, settled into a house at the foot of the Berea next to the garden, and officially started work on 1 January 1873. In September 1874 he married Louisa Ann Currie, with whom he had eight children.
Keit found the Durban Botanic Gardens in a neglected state, the plants placed haphazardly and without identifying names. He soon doubled the area under cultivation to nine hectares, laid out flowerbeds, rebuilt the paths, sowed grass on the banks to prevent erosion, and improved the soil with manure. In 1875 he established a nursery and two years later a pinetum which contained 27 varieties of conifer. By the end of 1875 the garden contained 670 plant species, though he was mainly interested in sea algae, palms and cycads. His botanical studies were limited mainly by weak eyesight and the lack of a microscope. None the less he described Agapanthus campanulatus 'mooreanus', a dwarf flower sometimes called Keit's blue lily. Another lily named after him is Littonia modesta var. keitii. In 1877 he collected plants at Noodsberg and Umvoti.
Keit continued the practice of using the garden as an experimental station for various crops and among others introduced new varieties of coffee, sugar cane, tea and tobacco. Though many of the plantation species that he promoted proved unsuitable, he successfully supplied 10 000 plants of Eucalyptus globulus, used mainly for swamp reclamation near Durban. He also exchanged plants with many botanic gardens all over the world. However, his duties during at least 1875-1880 included twice-daily meteorological observations, which prevented him from going on plant collecting trips. Furthermore, his efforts were undermined by drought, a shortage of labour, and a lack of money, so that the gardens again fell into a state of neglect. As a German he was furthermore not popular among the English speaking public.
At the end of 1881, following a re-organisation of the Natal Agricultural and Horticultural Society, Keit resigned as curator. He established a nursery, traded with overseas nurseries and in particular supplied large quantities of ferns to Germany. In 1883 he was appointed curator of Durban's parks and gardens and did much to beautify the town. His greatest achievement at this time was laying out and planting various parks and establishing a municipal nursery at Congella. In 1886 Robert Jameson* recommended him for an appointment as colonial forester, but nothing came of this. He was a quiet and reserved person. Keit Avenue in Durban was named after him.