Most bulbs prefer not to be disturbed and can be left in the ground for many years. But beware of overcrowding. When too many bulbs try to occupy the same space, they will be less vigorous and flowers will be fewer and smaller, an indication that it’s time to transplant them.
Spring - Once the foliage dies back or matures in the late spring or early summer, the bulb is dormant. You can tell the plant is dormant when the foliage is brown and papery and can easily be pulled free. Summer is the dormant period for spring bulbs. As the foliage dies back, the roots that nourish the bulbs also die back. With fall rains, the bulb comes out of summer dormancy and roots begin to grow again to provide the bulb nutrients and moisture. Once the spring bulbs enter dormancy, the time is right to dig the bulbs if needed. Some bulbs benefit from digging to divide the bulbs and spread them out over the bed.
If you lift your spring-flowering bulbs, they should be stored in a well ventilated place and replanted in the fall. Every five years daffodils and crocus should be dug and replanted to prevent overcrowding. The first sign of overcrowding will be a decrease in the flower size, uneven bloom and uneven plant height. When this occurs, dig, spread bulbs out and replant immediately.
Summer – Less hardy bulbs such as dahlias or begonias should be lifted each fall. It is best to lift after frost has blackened foliage, gently spade up the bulbs, being careful not to cut into the bulbs/tubers and damage them. If you prefer to lift the bulbs before frost has hit, you can dig your bulbs early and store them in a well-ventilated, frost-free area until they are dry. Just let the leaves remain on the bulbs until they become dry.
Most bulbs should be dried for about a week before you prepare them for storage. Pull any loose any remaining foliage, shake the bulbs gently to remove any clinging soil, dust them with fungicide powder to prevent rot and place them in unsealed paper bags or old nylon stockings with some dry peat moss to keep the bulbs from touching one another. Store them away from sunlight in a cool, dry basement, cellar, garage or shed at 60° to 65°F. Avoid temperatures below 50° or above 70°F unless different instructions are given for a particular bulbs. Follow specific storing instructions for tender bulbs, such as dahlias and begonias.