A plant bulb: an underground, rounded storage organ (e.g., tulips, lilies) that stores nutrients for overwintering and growth.
チューリップの球根を秋に植えると、春に花が咲く。
If you plant tulip bulbs in autumn, they bloom in spring.
園芸店でいろいろな色の球根が売られていた。
Various colored bulbs were being sold at the garden shop.
その多年草は球根で増えるため、手入れが比較的簡単だ。
That perennial spreads by bulbs, so it's relatively easy to care for.