The Best Time to Divide Asiatic Lilies

When to Divide

• Knowing when an Asiatic lily is ready to be divided is key to success. Lilies should be divided every few years, when they start to form large clumps of several stems. In addition, they need to be divided if they start to suffer from overcrowding, which causes them to become more prone to insects and to diseases such as mold.

Times of Year to Divide

• Two schools of thought predominate on when to divide Asiatic lilies. Most garden experts, as cited by the University of Washington Botanic Gardens, assert that fall is the best time to divide the plants, as with most other perennials. Dividing in the fall when plants are nearly dormant reduces chances of damage during and after during transplantation. However, also according to the UW Botanic Gardens, some sources indicate that summer is the best time of year to divide, since gardeners can then see the sizes and shapes of the plants being transplanted, and make design decisions accordingly. Plants can be divided either in the late fall or in mid-summer, depending on preference for minimizing plant damage or maximizing design options.

How to Divide

• To divide Asiatic lilies, dig up the root system by digging around the circumference of the plant, about 1 to 2 feet away from the stem. Using a sharp, flat shovel, carefully separate the clump of roots and bulbs into two or three smaller clumps, depending on the size of the roots. Immediately plant the divided sections in their new location. If planting them immediately is not possible, store them overnight with the roots in a bucket of water.

Post-Dividing Care

• It's especially important to make sure plants receive adequate water after dividing them. This will help them put down deep roots in their new location. Feeding Asiatic lilies after dividing in the fall is not a good idea. Plants put out tender growth when fed, making them more vulnerable to frost damage if such growth occurs right before frost. If dividing takes place in the summer, then feeding until six weeks before frost is appropriate.