Watsonia latifolia is an erect perennial geophyte that grows up to 1.5 m tall. It has a deep-seated short, solid, vertical underground stem covered with rough fibres, up to 60 mm in diameter.

Leaves 4-6, broad, lanceolate, 30-70 cm long, 4.7 cm wide or more, margins yellow, slightly thickened, midrib well defined in some plants but not well defined in others, arranged like a fan, some basal, those uppermost sheathing the stem, surface flat.

Inflorescence a spike that overtops the leaves, simple, rarely branched, many-flowered; outer bracts about 25 mm long, lower ones clasping the stem; inner bracts slightly smaller. Flowers blood-red, 60-80 mm long, curved; perianth tube with the basal part erect, exserted from the bracts, about 20 mm long, the arched part horizontal, 18-20 mm long, about 8 mm wide (when dried); tepals lanceolate, about 20 mm long, 5-8 mm wide and ascending or spreading. Filaments attached to the tube where it becomes wider, 28-35 mm long, arched below the upper tepal, exserted from the tube; anthers about 10 mm long and violet. Style divided and overtopping the anthers when mature, arching over the filaments. Flowering takes place between December and February.

Capsules oblong-fusiform (spindle-shaped), 14-20 mm long, about as long as the bracts.