Crinum macowanii may grow to 1 m annually when in flower from a large bulb. The leaves are channelled, strap-like and may have wavy edges. The flowers grow on short pedicels that emerge from the top end of the sturdy flower stalk, enveloped at their base by large papery bracts. There may be up to 25 flowers on one stalk.
Flower colour is white with pinkish stripes running down the central keels of the tepals. The flower is funnel-shaped with tube length varying between 3 cm and 11 cm. The stamens arch downwards, the anthers black.
Blooming happens in spring through summer. Flowers are sweetly scented at night, opening in the evening and lasting for about two days (Manning, 2009).