Air potato (Dioscorea bulbifera) — the aerial yam — is a climbing vine of the yam family grown not for an underground tuber but for the knobbly, potato-like bulbils it swells in the axils of its leaves. Each aerial yam ranges from marble- to fist- sized, with a rough, warty, greyish-brown skin over pale cream to faintly purple flesh that cooks up dense, floury and mild — closer to a starchy yam or potato than to anything sweet. Edible cultivars are peeled and boiled, roasted or fried much like a yam; the wild and many feral forms are intensely bitter and mildly toxic, and are eaten only after careful peeling, slicing and long soaking or repeated boiling to leach out their bitterness. It is this habit of carrying its crop in the air, rather than any flavour of its own, that sets the aerial yam apart from its earth-bound relatives.