Why, When, How To Divide Perennials

Multiply By Dividing: Why, When, How To Divide Perennials

Multiply By Dividing: Divide Perennials For More & Better Plants

Why Divide Perennials

Perennial plants are terrific – plant them once, feed and water them regularly, and they offer flowers, fruit and foliage for years. However, there comes a time when many perennials start to look a little puny. If your favorite perennial is fading out – the flowers are small, sparse and the plant’s body looks like a size 8 foot shoved into a size 4 shoe – it is probably time to dig, divide and replant. Unfortunately, however, not all perennials can be divided.

Woody perennials, such as roses, mock orange or hydrangea, have a root system that needs to stay intact for optimal growth. Judicious pruning and fertilizing would help to rejuvenate these plants. Plants with fibrous or multibranched root systems, ones on which each branch sends 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.

Why, When, How To Divide Perennials, peonia

How To Divide Perennials

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

The process of dividing a plant looks challenging and is similar to doing aboriginal surgery.

  • First, use a garden fork or spade to dig around the entire base of the plant and loosen it from the soil. The entire root ball of the plant should be leveraged out of the ground.
  • Next, plunge the spade into the heart of the plant. Press the blade down to cut entirely through the plant’s roots and rock gently back and forth. This should create a clear schism; the rocking motion separates the root ball into two pieces.
  • Now, use the utility knife to cut through any tangled roots and separate the plant thoroughly. If the plant is enormous, these halves can be halved again, creating four plants from one. Keep as much of the root ball intact as possible, but tease apart girdled roots.
  • Trim off any blooms and replant the divisions into well-prepared soil, ensuring that the new plant is placed in the ground at the same level as the original plant.
  • Water the new plants in mulch well, and keep the newly planted divisions 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 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 dividing the iris, trim the foliage down to a 3″ length; daylilies should keep their foliage at full length, trimming off only yellowing or browning ends. As with other perennials, plant at the same depth as the original plant and water well.

Why, When, How To Divide Perennials, iris

When To Divide Perennials

The best seasons to divide plants are early spring and late summer through fall, from August through November in the midwest. Fall divisions need to be watered consistently until the first heavy frost hits. Roots grow slowly, in late fall until the ground freezes and the plant goes completely dormant.

Enjoy The Rewards of Dividing Perennials

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.

Why, When, How To Divide Perennials, monarda

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