Trichodiadema mirabile is succulent plant of the genus Trichodiadema, native to the Western Cape Province, South Africa, where it is known from the Laingsburg area and especially from south-facing slopes.

The leaves are erect, stiff and papillate, and each leaf is tipped with dark-brown, erect-inclining bristles.

[2] It very closely resembles Trichodiadema orientale, a species from the Eastern Cape, which however has 5 locules, longer papillae on its bladder cells, and has flowers that are more pinkish-white (sometimes white with pinkish petal tips).

Trichodiadema orientale also has longer flower stalks, while those of T. mirabile are so short that they are usually not visible.

Trichodiadema mirabile, T. orientale and T. hallii are the only three species in the genus to have erect-inclining diadem bristles.