The Alabama Cooperative Extension System says that early spring before new growth or after foliage has died in fall are the best times for dividing and transplanting iris. Dividing is the process of separating one plant into two or more smaller plants.
Before transplanting iris bulbs to the new location make sure the soil will drain water away well. Iris roots are prone to root rot in poorly draining soil. Consider using raised garden beds if soil cannot be amended to drain well.
The iris leaves should be cut back to 1/3 their height before digging up the roots, also known as rhizomes. If desired the iris plant can be divided into two or more plants. Only healthy rhizomes should be kept and transplanted.
Newly planted iris bulbs will need enough space between them for air circulation. This helps prevent diseases. The plant should be watered well after it is transplanted to help the soil settle.