The name Coleus is derived from the Greek koleos, meaning ‘a sheath’, and refers to the fused stamens of the type species for the genus, and a character that at one time was thought to be diagnostic for this genus. Its species name honours Dr John Kirk (1832-1922) who collected a specimen of our species in Manganja Hills. Kirk was a medical doctor who was also a keen botanist. He was born in Scotland, joined Livingstone’s second expedition where he made many field drawings and was among the first to photograph the vegetation in the Zambezi Valley. He collected many plant specimens and has many species named after him, including Dombeya kirkii, Kirkia acuminata, Diospyros kirkii, Cleistochlamys kirkii and Maerua kirkii.

Coleus kirkii previously was placed in the genus Pycnostachys, the name meaning ‘dense spike’, from the Greek pyknos meaning ‘dense’, and stachys actually ‘an ear of corn’ but in botany ‘a spike’ and referring to the inflorescences. It was moved into the genus Coleus in 2019 after molecular studies on Plectranthus and closely related genera by Paton et al showed that the old definition of the genus Plectranthus did not have a single common ancestor, and that it contained two distinct clades separate from Plectranthus. The one clade including the type species of the former genus Coleus, which led to the re-instatement of the genus Coleus, and the other that is now recognized as the new genus Equilabium. A new, smaller, Plectranthus was redefined. The study also showed that the genera Pycnostachys, Anisochilus, Leocus and some species of Solenostemon belong inside the Coleus clade. 

When it was moved into Coleus, this species lost its previous species name reticulata because there is already a Coleus reticulatus in western Africa. Reticulata means ‘netted’ or ‘a network’ in Latin, and referred to the veins, which are clearly visible on the underside of the leaf. Our species name reverted to the next oldest valid name, Pycnostachys kirkii, which had been sunk into synonymy under Pycnostachys reticulata.

All species of Pycnostachys have been transferred to Coleus. Only 3 of them occur in South Africa: Pycnostachys reticulata now Coleus kirkii, Pycnostachys urticifolia now Coleus livingstonei and Pycnostachys coerulea now Coleus stenostachys. At Kirstenbosch we grow Coleus kirkii and C. livingstonei, the latter is commonly known as the hedgehog sage, blue boys, nettle-leaf pycnostachys, dark blue pycnostachys, ystervarksalie (Afr.), amadata or unkungwini (Zulu). Its leaves are markedly different, greener, broader, almost triangular with rounded teeth and the flowers are a bright gentian blue or pale blue or white. It occurs in moist places along grassy streambanks and forest margins in Limpopo, Mpumalanga as well as Zimbabwe, Mozambique, Eswatini and Tanzania.