Gloriosa superba is a deciduous, summer-growing climber up to 1.5 m tall, with tuberous roots. The slender stems are produced annually and are upright to scrambling and can grow up to 4 m long. Tubers sprout in spring, and a tuber sends up 1 to 6 stems. The leaves are shiny, bright green and are tipped in a tendril, which will cling to anything it touches. The stems die back in late summer and the tubers are dormant during winter.

The showy flowers are borne in summer (November to March) and are usually bi-coloured yellow and orange-scarlet, ageing a deeper shade of orange-red to purple. There is also a pure yellow form. The flowers are borne on long pedicels on the upper parts of the stems. They are nodding, i.e. they are presented up-side-down, with the ovary at the base, the stamens in the middle and the petals at the top. There are 6 free petals, and they are bent backwards (reflexed) so that they are pointing upwards. With their wavy, curling margins, and fiery colours, they really do look like flames. The stamens are large and prominent, and are presented in a ring around the flower, like the spokes of a wagon wheel radiating out around the flower, each tipped with a large anther. The base of the flower is made up of the large, shiny, green ovary tipped by the style, which is bent sharply outwards from the point of attachment at the tip of the ovary, and tipped by a stigma with three short arms.

The colours of the petals in the bi-coloured forms, indicate the stage of development of the flower. The flower buds are yellow or greenish yellow. As the flower opens and matures, the yellow and orange-red colours of the petals develop and deepen. The stigma is receptive for 3 days when the petals show the orange-red tips, yellow middle and greenish base. In pollinated flowers the petals lose the greenish colour at the base, and the top half of the petal remains orange-red and the middle to base is yellow. As the flower ages, the petals become entirely orange-red and the shade darkens. Eventually they wither and turn brown. From tight bud to withering flower takes about 2 weeks. The style and stamens also turn brown and shrivel up, while the green ovary at the centre of the flower, enlarges as the seeds develop inside.

The fruit is a large, leathery, 3-valved capsule, taking 6–10 weeks to ripen. It splits to release large, rounded, 4–5 mm in diameter, red seeds, with a thin fleshy outer layer.