Plectranthus grandidentatus is a trailing perennial with soft, hairy stems reaching heights between 30 cm and 60 cm. The broadly ovate and semi-succulent leaves taper to pointed or rounded tips. They have conspicuously toothed margins. Leaf surfaces are velvety from a dense covering of hairs. There is also a conspicuous pattern of veins recessed on the upper leaf surfaces. The lower leaf surfaces are covered in red to brown gland dots. The leaf petioles are up to 8 cm long.
The plant grows as underbrush on dry rocky slopes and in wooded kloofs in the eastern parts of South Africa from the Eastern Cape to Limpopo. It is also found in Zimbabwe and beyond in tropical southern Africa (JSTOR; www.plantzafrica.com).