Perennial herb. Rootstock tuberous, ovoid to spindle-shaped, up to 200 x 100 mm, bark brown, flesh bright yellow. Stems annual, finely ridged, sparsely hairy, up to 2 m long, climbing in trees, shrubs and grasses, also prostrate if no support is available, cut stems exude no sap. Leaves broadly ovate to pentagonal in outline, base heart-shaped, unlobed to deeply palmately 3-5-lobed, up to 110 x 75 mm, bright green above and paler below, densely hairy on both sides, especially on the prominent veins beneath, leaf edges finely toothed, crushed leaves non-aromatic. Leaf stalks hairy, up to 60 mm long. Tendrils usually with two branches.

Flowers either male or female, both appearing on the same plant (monoecious), greenish white to greenish yellow. Male flowers more or less 5-11 in about 50 mm long inflorescences, petals 3.5-5.0 mm long, stamens and pollen orange. Female flowers solitary, petals 6-8 mm long, stigma orange. K. hirtella flowers from October to April, but mainly in January.

The fruiting time is from November to April, but also mainly in January. Fruit cylindrical to somewhat spindle-shaped, rounded at the base, tip beaked, up to 100 x 25 mm, smooth and hairless, green with pale green or white speckles longitudinally arranged, becoming yellow to bright orange-red, splitting lengthwise when ripe, pulp orange to red, bright red around seeds. Seeds 18-20 per fruit, up to 6 mm across, subglobose, edges prominent, smooth, dark brown, drying grey to whitish.