Diosma hirsuta, commonly rooiboegoe (red buchu) in Afrikaans, is a shrub growing to 50 cm from a woody rootstock that resprouts after fire.
The plant's alternate leaves are narrow, needle-like and spine-tipped; hairy when young. A heavy buchu scent is exuded, enhanced when the leaves are crushed.
The flowers grow in short racemes at branch tips, each with five rounded petals that tend to persist as the fruits develop. An interesting angular red pattern made by the ovary is visible at the base of the flowers.
The five-chambered fruit, shiny green in the photo, has a horn on each chamber. This shape recurs in other Diosma species with some variations.
The species distribution is along the southern coastal region of the Western Cape, inland to Nieuwoudtville and eastwards to Ladismith in the Little Karoo and Humansdorp in the Eastern Cape. The habitat is sandstone and clayey slopes and flats.
All 28 Diosma or bitterboegoe species are found in the fynbos. This plant was seen during October in the Fernkloof Nature Reserve, next to the coastal town of Hermanus (Manning, 2007; Bean and Johns, 2005).