What is the term for a short, starchy underground stem covered with scales?

The correct term for a short, starchy underground stem that is covered with scales is a bulb. A bulb is a specialized storage organ that consists typically of a short stem surrounded by fleshy leaves or scales, which contain nutrients that support the plant's growth. Bulbs are commonly found in plants like onions and tulips.

While other terms may appear similar, they refer to different structures. A tuber, for example, is an enlarged part of an underground stem that stores nutrients, but it does not have the layered structure typical of a bulb. Rhizomes are horizontal underground stems, allowing plants to propagate and spread, but they do not exhibit the characteristic scaly covering. Corms, while similar to bulbs, are solid structures that primarily consist of a swollen stem base and lack the layered scales associated with bulbs. This distinction in structure and function is essential in understanding plant biology and how various plants store energy.