Brachystelma buchanani is an erect or procumbent perennial with annual stems, growing from a large fleshy tuber (caudex). The leaves are ovate-elliptic. The flowers are terminal in a 20-30-flowered umbel and give out an intense cow-dung-scent from midday until the early afternoon and when in full bloom attract flies in large numbers throughout the hotter part of the day, if the weather is sunny. The corolla up to 25 mm in diameter, is flat and wheel-shaped, blackish purple, and hairless.