In the Garden
Amy Jordan, Special to The Gazette
Thursday, September 11, 2008
Take advantage of the cool weather we are having and divide perennial flowers.
Many perennials need to be divided every 3 to 5 years to maintain vigor, including daylilies, Asiatic lilies, bearded and Siberian iris, and some hostas.
Dividing perennials could be done to control the size of the plant, rejuvenate the plant to improve its performance or to increase the number of plants in your landscape.
Plants often signal when they need more room. Flowers become fewer or smaller, leaves look crowded, and a dead spot may form in the center with shoots growing up around it. These are all signs plants need to be divided.
Although many plants can be divided in early spring as new growth is emerging, a good rule of thumb is to divide spring and summer blooming perennials in the fall, and fall blooming perennials such as chrysanthemums and asters in the spring.
Late summer to early fall divisions allow plants time to adjust and become settled in before cold weather stops root growth, which typically happens in November. Iris should be the first on your division schedule because they are more prone to heaving out of the ground in the winter if their roots are not well established.
Peonies can also be divided in the fall, but they prefer to be left undisturbed. They could be left in the same spot indefinitely without a decline in performance. But if you need to relocate a plant or want to put some in another spot, now is the time to do it. Keep in mind that it may take 3 years for the plant to recover in size and flower bloom.
To divide plants:
• Thoroughly water plants that will be divided a day or two before they are dug.
• Plants may be easier to handle if the foliage is cut back to within about 6 inches from the ground.
• Dig around and under the plant and lift it from the ground. Carefully remove the soil from the root system. Washing it off with water is often the easiest method to do this.
• After the soil is gone from the root system, many plants can be easily separated into sections. A spading fork or sharp knife could also be used. Divisions should be about the size of a head of cauliflower.
• Prepare a planting hole for the divisions.
• Set the new plants into the planting hole at the appropriate depth. Daylilies, hosta, and most other perennials should be the same depth as what they were growing. Iris rhizomes should be at the soil level, not below. Peony eyes should be no more than one inch below the soil surface.
• Backfill with soil, firm it around the plant, and water well. Reset peonies and iris if they settle deeper that what was discussed above.
The number of flowers may be reduced the first year after dividing, but will return to normal until the plants need to be divided again.