Tiger lilies are perennial bulbs. They should be dug up and transplanted every few years to allow for efficient blooming. Transplanting is most successful if done in the early fall or late winter.
Wait for the right time
If you decide to transplant tiger lilies while they are in bloom during spring and summer, clip off the flowers so the plant's energy goes toward storing food for the winter. However, transplanting is best in early fall when the leaves' foliage is yellowing or in late winter right before they begin to grow again. At this time, the bulbs are most easily divided.
Dig up the tiger lilies
When digging up the plant, pierce the ground with the shovel a few inches away from the center of the plant. Use the end of the shovel to pry up the bulb gently. If you are unsure of the bulb's location in the soil, dig gently to avoid damaging the plant. The main bulb resembles a large clove of garlic. Remove the smaller bulbs that have formed on the main bulb. They should be easy to pull right off.
Transplant the tiger lilies
Large bulbs should be planted in groups of at least three. Plant them 8 to 10 inches apart and 4 to 6 inches deep in a well-drained and nutrient-rich soil. Smaller bulbs should only be planted 2 inches deep. Once you cover the bulbs with soil, give the newly planted lilies a good soaking so the soil sets around them.