A hyacinth bulb is the short, fleshy base of the hyacinth plant, which is a fragrant, decorative plant commonly found in gardens. The hyacinth bulb functions as a food storage organ while the plant is dormant. The bulbs are normally planted in the fall and bloom in the spring.
The flower bulb's base contains food reserves to help the plant make it through adverse conditions. During the growing season, roots come out of the bottom of the base, and new stems and leaves sprout from the top.
The botany term for plants that form these underground organs, which include bulbs, tubers and corms, is geophyte.