There are many perennial flowers that spring forth from bulbs rather than seeds. Some of the most common are tulips, lilies, daffodils, crocuses, hyacinths, iris, dahlias, alliums, caladiums and gladioli. Bulbs self-propagate underground and if left unattended, become easily overcrowded, causing a decrease in bloom production. As a general rule, bulbs should be dug and separated every two to three years. Fall or early winter, when bulbs are dormant, are the best times to dig and separate bulbs.
Cut back foliage a few inches above the soil, once blooms have died back and foliage has shriveled or turned yellow and wilted, indicating that the bulbs have become dormant. Do not dig too early in the fall, because bulbs need time to store up nutrients to aide in next year's growth. It is better to wait until early winter, so they have time to prepare for the following season.
Mark a large circle around each plant and carefully dig down below the bulbs, which can be from 4 to 8 inches deep. Be sure to dig down far enough to remove the whole bulb with its root system intact.
Shake away any loose dirt from the clump, holding the stem in one hand and the soil clump in the other. This allows you to better see the bulbs. If clumps are too big, soil can be washed off by gently pouring water over the top.
Separate the bulbs gently with your fingers. They should come apart easily. If root tangles from other plants prevent separation, they can be carefully clipped with pruning shears. Do not cut bulb roots or try to cut bulbs apart with a knife.
Replant bulbs immediately, if possible. Bulbs can be stored in a cool, dry place, but should be planted as early as possible in spring. As a general rule, bulbs should not be stored over three months. Check stored bulbs before planting and discard any that show signs of rot.