How do I divide perennial plants?
Splitting overgrown clumps to rejuvenate them and get free plants, and when each type should be divided.
- Difficulty
- intermediate
- Time
- 1 hr
- Read
- 2 min
Short answer
Lift the clump, split it into pieces each with roots and shoots, discard the woody dead centre, and replant immediately. Divide spring-flowering plants in autumn and autumn-flowering ones in spring — roughly the opposite of when they flower.
Many perennials die out in the middle as the clump ages, because the centre is the oldest and most congested part. Dividing removes that and gives you several vigorous young plants from one tired one.
What you'll need
- Spade or garden fork
- Old knife or saw (optional)
- Two forks (optional)
- Watering can (optional)
Step by step
- Divide every three to five years, or when the centre dies out.A bare woody middle with growth only around the edge is the plant telling you it needs dividing.
- Choose the season opposite to flowering.Spring-flowering plants in autumn, summer and autumn-flowering plants in spring. It avoids disturbing them when they are putting energy into flowers.
- Water the plant well the day before.It makes lifting easier and reduces the shock of the whole process.
- Lift the entire clump with a fork.Work around the edge and lever it up, keeping as much root as you reasonably can.
- Split it into pieces, each with roots and shoots.Fibrous clumps can be pulled apart or cut. Tough woody ones need two forks back to back, or a spade or old saw.
- Discard the old woody centre.It is the least vigorous part and will not perform. The outer sections are the ones worth keeping.
- Replant immediately at the same depth.Divisions dry out fast. If you cannot plant straight away, pot them up or heel them into soil temporarily.
- Water in well and keep watered for several weeks.They have lost root and cannot yet support their top growth. Cutting back the foliage by half also reduces the stress.
Tips
- Divisions make excellent gifts and swaps. A single overgrown clump can produce five or six good plants.
- Some perennials dislike disturbance — peonies, hellebores and oriental poppies among them. Check before dividing rather than assuming.
- Ornamental grasses are best divided in spring, not autumn. Autumn division often fails because they do not root before winter.
Common mistakes
- Replanting the old centre — It is the oldest, most congested and least vigorous part, and it will continue to perform poorly.
- Letting divisions dry out before replanting — Exposed roots dry within minutes on a warm day and the division may not recover.
- Dividing while the plant is flowering — It is at maximum stress and putting everything into the flowers. Divide before or after, not during.
Questions people ask
When should I divide perennials?
Roughly opposite to when they flower: spring-flowering plants in autumn, summer and autumn-flowering plants in spring. Grasses are best divided in spring regardless.
Why has the middle of my plant died out?
It is a mature clump that needs dividing. The centre is the oldest and most congested part. Lift it, split it, discard the woody middle and replant the vigorous outer sections.