Many border perennials grow into ever-bigger clumps that flower less in the middle and slowly run out of steam. Lifting and splitting them every few years rejuvenates the plant and, best of all, gives you several new ones for nothing.
Why bother
An old clump often dies out in the centre, leaving a ring of growth around a bald middle. Dividing it removes the worn-out heart and replants the vigorous young outer pieces, so the plant flowers freely again instead of fading.
When to do it
Spring, as growth is just starting, is ideal for most perennials, especially late-flowering ones. The soil is warming, the days lengthening, and the divisions have the whole season to settle in before they have to flower.
- Lift the whole clump with a fork.
- Shake or wash off enough soil to see the crown.
- Split it into fist-sized pieces, each with roots and shoots.
How to split them
Soft, fibrous clumps such as asters pull apart by hand or with two forks back to back. Tough, woody crowns may need a spade or even an old bread knife. Discard the tired central section and keep the healthy young outer growth.
Replant promptly
Get the divisions back in the ground, or potted up, before the roots dry out, at the same depth they were before. Water them in well and keep them moist through their first few weeks, and one tired plant becomes a generous gift to the whole garden.