Hardy bulbs sometimes need to be divided. After a number of years in the garden, some daffodils and other bulbs produce offsets that cluster around the base of the parent bulb. Crowded foliage and diminished flowering are signs that the bulb clumps need to be divided. After the leaves die back, dig up the bulbs and carefully separate the offsets from the parents. Replant the bulbs immediately or store them in a cool, dry place until bulb-planting time in the fall. Plant the offsets twice as deep as their height; don't plant them as deep as mature bulbs. Small offsets will take a few years to reach blooming size.
Some corms, such as gladiolus, crocus, and freesia, produce small structures called cormels around their base, similar to the offsets of bulbs. These can be removed and replanted to increase your supply. When plants are dormant, remove the cormels. Immediately replant cormels of hardy plants like crocus and colchicum. For tender plants like gladiolus, store the corms and cormels in a cool, dry place over winter and plant in spring.
For scaly bulbs like lilies, you can dig the bulbs in spring and remove the small scales that form around the outside. Replant immediately.