H.M. Louisa ("Lulu") Bolus (born Kensit), daughter of William Kensit and his wife Jane Stuart, was educated at the Girls' Collegiate School in Port Elizabeth and matriculated in 1898. The next year later she was awarded a teacher's diploma at the Cape Town Teachers' Training College. She continued her studies at the South African College, Cape Town and in 1902 was awarded the degree Bachelor of Arts (BA), with honours in literature and philosophy, by the University of the Cape of Good Hope. Meanwhile she had begun to assist her great-uncle, Harry Bolus*, with his private herbarium of South African plants, and in January 1903 he appointed her as herbarium assistant. During the next few years she assisted him in the compilation of his work on the family Ericaceae (heaths) for the Flora capensis (1905) and Volume 2 of his Icones orchidearum Austro-Africanarum extra-tropicarum... (1911). Her first paper, describing a new species of vygie, Mesembryanthemum pillansii, was published in a book by E. de Wildeman in Belgium in 1908. From 1907 to 1909 she and Harry also assisted Dr Selmar Schonland*, curator of the Albany Museum herbarium, with the identification of the more difficult genera of flowering plants of the Eastern Cape.
Following Harry's death in 1911 Louisa completed and edited Volume 3 of his Icones orchidearum..., which was published in London in 1913. Frank Bolus*, Harry's youngest son and a cousin of Louisa's father, painted nine plates for this volume. Frank and Louisa were married in 1912, but had no children. The two of them published a "Key to the flora of the Cape Peninsula" in the Annals of the Bolus Herbarium (1914-1915, Vol. 1, in 3 parts) and, with R. Glover and others, described the flowering plants and ferns collected in German South West Africa (now Namibia) by the various Percy Sladen Memorial Expeditions in the same journal (1914-1915, Vol. 1, in 3 parts; 1920, Vol. 3). With A.M. Greene, Louisa also edited Harry Bolus's book The orchids of the Cape Peninsula (Cape Town, 1918).
Harry left his herbarium and botanical library to the South African College (from 1918 the University of Cape Town) and made provision in his will for their maintenance and extension, on the condition that Louisa would remain its curator for life. As a result she dedicated her entire professional life to the herbarium, until her retirement in 1955, at the age of 77. During this long period she described more new South African plant species (probably around 1700) than any other local botanist, but never attempted any real synthesis. From 1914 to 1928 many of her descriptions were published in the Annals of the Bolus Herbarium, which she edited from 1918 to 1925. Some of her later descriptions were in Latin and, as she was not herself a botanical artist, were not accompanied by illustrations, making them accessible to botanical specialists only. Her botanical interests initially matched those of Harry Bolus, including mainly the heaths, orchids, and vygies. Between 1914 and 1928 she published a series of descriptions of new species under the title "Novitates Africanae" in the Annals of the Bolus Herbarium and continued the series in The Journal of Botany (London, 1928-1934). In another series of articles, "Plants new and noteworthy", published in South African Gardening and Country Life (1927-1935) she described both new and known species. From the late nineteen-twenties until the end of her life she gave much attention to the genus Mesembryanthemum and allied genera, on which she became a world authority. Her "Notes on Mesembryanthemum and some allied genera" initially appeared in the Journal of the Botanical Society of South Africa (1927) and South African Gardening and Country Life (1927-1930), then as publications of the University of Cape Town (1928-1958), and subsequently in the Journal of South African Botany (1959-1969). In these notes she described numerous new species and some new genera, as well as keys to the genera and other groups of species. Some of her descriptions of other plants appeared in The Flowering Plants of South Africa (1927-1968). She had rather rigid views on how botanical studies should be carried out, based on those of Harry Bolus, and as a result attracted few co-workers. With regard to the Bolus Herbarium too, she showed strong resistance to inevitable changes.
Louisa spent much of her time fostering an interest in the South African flora and other aspects of nature in both children and adult lay persons. For example, after the foundation of Kirstenbosch in 1913 she often conducted groups of children around the garden. She also wrote popular articles for journals such as Nature Notes, South African Gardening and Country Life and the Journal of the Botanical Society of South Africa. Many of these dealt with the flora and birds of Kirstenbosch. Other publications included a textbook for schools, Elementary lessons in systematic botany based on familiar species of the South African flora (Cape Town, 1919, illustrated by Mary M. Page), and the popular works A book of South African flowers (Cape Town, 1925, with illustrations by D. Barclay and E.J. Steer) and A second book of South African flowers (Cape Town, 1936, with illustrations again by Barclay and Steer). In her younger years she was an active plant collector in the mountains around Cape Town, but a serious ankle injury in middle age put an end to such field work.
Louisa was a foundation member of the Botanical Society of South Africa, which was created in 1913 to provide funds for the development of Kirstenbosch, and served on its council until 1956. In 1907 she joined the Philosophical Society of South Africa as one of its very few female members, remained a member when it became the Royal Society of South Africa in 1908, and was elected a Fellow of the latter in 1920. By that time she had already been elected a Fellow of the Linnean Society. She joined the South African Association for the Advancement of Science in 1905 and became a life member. From 1922 she was a life member of the Cape Natural History Club and one of its consultants on flowering plants. She was a foundation member of the Wild Life Protection Society and for some time a member of the Mountain Club of South Africa. Stellenbosch University awarded her an honorary Doctor of Science (DSc) degree in 1936. In 1940 the South African Biological Society awarded her the Senior Captain Scott Memorial Medal. Some time after her retirement she was elected a member of the International Organisation for Succulent Plant Study, and when the African Succulent Plant Society was founded in 1966 she was elected as vice-president. As part of her extensive European travels she visited the Royal Botanical Gardens at Kew several times from 1906 onwards, and also visited herbaria in Uppsala and Vienna.
After her retirement as curator in 1955 Louisa continued to visit the Bolus Herbarium, working in a specially reserved area, and was appointed by the University of Cape Town as an honorary reader in plant taxonomy. She continued her botanical studies until shortly before her death. The genera Kensitia and Bolusanthemum, and the species Geissorhiza louisabolusiae, were named after her.