Not all perennials can be divided. Woody perennials, such as roses, mockorange or hydrangea, have a root system that needs to stay intact for optimal growth. Judicious pruning and cloning by way of cuttings rather than divisions would help to rejuvenate and duplicate these plants. Plants with fibrous or multibranched root systems, each branch sending up one or more flowering stalks, are the best candidates for division.  These plants include peonies, iris, ornamental grasses, ferns, monarda, mints, chives, hostas and daylilies.

 

The tools needed to divide plants are fairly basic: a durable, sharp spade and a utility knife will do the job nicely.  Large clumps of ornamental grass may also require a Sawzall that will slice through the tangle of roots and soil.

 

Doing divisions looks brutal, and is similar to doing surgery on the plant.  First, use a garden fork or spade to loosen the plant from the soil. Next, plunge the spade into the heart of the plant. Press the blade down so that it cuts completely through the plant's roots, and rock gently back and forth. This should create a clear schism, and rocking will leverage one half of the plant out of the ground.  Use the utility knife to cut through any conjoined roots and separate the plant completely.  If the plant is extremely large, the halves can be halved again, creating 4 plants from one. Keep as much of the root ball intact as possible, but tease apart roots that are girdled.  Trim off any blooms and replant the divisions into well-prepared soil.  Water the new plants in, and keep them watered and protected from strong winds until new roots develop and anchor the plants in the ground. This should take about four to six weeks.

 

Daylilies and iris divide themselves naturally. Both daylilies and iris send up fans, or leaf clusters attached to a fingerlike root. Use the same method described above to separate the fans daylily and iris plants produce. After division, trim the foliage of the fan down to a length of 3", replant at the same depth at which the original plant was positioned, and water in.

 

The best seasons in which to divide plants are early spring and late summer through fall, from August through November. Fall divisions need to be watered consistently until the first heavy frost hits. Roots grow, albeit slowly, in late fall until the ground freezes and the plant is completely dormant. What are the rewards for these efforts?  Both the original plant and the divisions will show greater vigor and send out more blooms per plant., plant divisions are exact duplicates of their parent plant so one favorite plant can be replicated throughout the garden, and the cost to expand the garden is time and effort rather than dollars and cents.