Some plants over-winter by means of an underground structure called a bulb. During the growing season, the leaves of the plant send sugars and carbohydrates created through photosynthesis down into the bulb. When the process is completed, the leaves die back to the ground and the bulb goes dormant. In the spring (for most bulbs anyway), the bulb begins to grow again and goes through the cycle again.

Here are the common genera of "bulbs" found in home landscapes in the temperate zones of North America: