Aloe hardyi is a fast growing aloe forming solitary rosettes hanging from cliff faces. Its roots are cylindrial and up to 6 mm in diameter and form a network which anchors the plant in crevices on cliffs. The stems are simple or occasionally branched from the base to form loose hanging leaf clusters with stems up to 1,5 m long. The leaves are pendulous or curve downwards, and are borne in dense rosettes, up to 400-700 mm long and 50-80 mm in diameter, at the ends of branches. During the rainy season the leaves spread slightly and curve inwards, but during the dry season they draw together again. The skin (epidermis) of the leaves is bluish to pale green with a powdery bloom and with a reddish colour during the dry season or during prolonged droughts. The leaves on young plants are distichous (regularly arranged one above the other in two opposite rows, one on each side of the stem) for the first two years. The inflorescence is a simple raceme 450-700 mm long in total. At first it hangs but then curves upwards so that the flower-bearing part, which is up to 200 mm long and conical in the bud stage, stands almost upright. The flowers are spreading to sub-pendulous, with orange-red, green-tipped tepals 25-40 x 7 mm. The fruiting capsule is ascending-spreading and 25 x 7 mm. The seeds are angular, 3 ´ 2 mm and grey, and there are about 55-70 per capsule.

Flowering occurs mainly during midwinter (July, southern hemisphere).