Are the perennials in your landscape in decline? Are they blooming less than they used to even though you fertilize and water them regularly? Is the foliage stunted and do the plants lack vigor? It may be that your plants have become too crowded and are in need of dividing.
Rick Durham, consumer horticulture extension specialist at the University of Kentucky, gives us information on dividing perennials.
Most perennials need to be divided every three to five years, some even more often. Keeping plants growing vigorously by dividing them is one way to prevent problems with insects and disease. Vigorously growing plants are often able to tolerate or resist attack by pests. Digging and dividing perennials regularly would be a cultural practice in line with Integrated Pest Management, or IPM, an approach that allows homeowners to have a nice looking landscape using a minimum of pesticides.
Fall and spring are the times for dividing most perennials. As a general rule, perennials that bloom in the spring, such as daylilies, peonies, and bearded iris, should be divided in the fall. Perennials that bloom in the summer and fall, such as chrysanthemums, hostas, and asters, should be divided in the spring. The technique is pretty much the same regardless of the time of year. Dividing is best done as plants end their growth and begin dormancy in the fall or before regrowth occurs in the spring.
When digging perennials, loosen the soil around the plant with a shovel or garden fork to allow the plant to be lifted with a good portion of its roots system. Shake or work the root ball with your fingers to dislodge as much soil as possible. This will allow you to see the growing parts of the plant, newer growth is usually toward the outside of the clump.
Next, pull or cut the clump apart leaving a mixture of old and new growth with each division. Trim back the foliage to two to three inches and remove any broken or excessively long roots. Plant the division at the same depth as it was previously growing. You will likely have extra plants, so share or exchange some with neighbors or friends.
After planting, apply a layer of organic mulch and keep the plants well watered for several weeks until roots have become established. Fertilize the transplants only sparingly until growth resumes. Some plants will respond with increased bloom the following season, others may take a season or two to return to their full potential.
Log on to http://www.ca.uky.edu/agc/pubs/ho/ho67/ho67.pdf for more information on propagating plants, or call the Extension Office and ask for publication HO-67, Propagating Plants, In and Around the Home.
Contact the Franklin County Cooperative Extension Service at 502-695-9035 by phone or email firstname.lastname@example.org for more information about lawn, garden, and home landscaping. Educational programs of the Cooperative Extension Service serve all people regardless of race, color, sex, religion, disability or national origin.
Adam Leonberger is a Franklin County extension agent for horticulture.