Tuber
Plant's underground storage organ formed by the swelling of an underground stem which produces buds and stores photosynthate metabolites/nutrients, forming a seasonal perennating organ, e.g. a potato
Tubers are a type of enlarged structure that plants use as storage organs for nutrients, derived from stems or roots. Tubers help plants perennate (survive winter or dry months), provide energy and nutrients, and are a means of asexual reproduction. Stem tubers manifest as thickened rhizomes (underground stems) or stolons (horizontal connections between organisms); examples include the potato and ... Wikipedia