When a perennial goes bare in the middle after a few years and only shoots at the edge, that is no cause for worry but an invitation: it wants to be divided. Dividing rejuvenates the plant, keeps it vital and gives you free replacements for new bed sections or to give away.
Two questions decide success: which perennial is divided when and how you go about it. This article answers both, so your perennials grow back stronger after dividing than before.
Why and when to divide
Many perennials keep growing outward and die off inside, the classic bare centre. Others simply get too big over the years or bloom less. Dividing fixes both: you remove the old core and replant the vital edge pieces.
The right time depends on flowering. Rule of thumb: what blooms in spring or summer you divide in autumn. What blooms in autumn you divide in early spring. That way you never catch the buds and the plant has the longest recovery after the operation.
How to divide correctly
The dividing itself is simple and forgiving. The only thing that matters is that each piece keeps its own roots and at least one growth bud. Small, weak splinters go on the compost, sturdy edge pieces are replanted.
Dig up the clump
Push the spade in a wide arc around the plant and lift the whole clump out of the ground. Shake off loose soil so you can see where to separate.
Remove the bare centre
Cut out the old, bare core and throw it away. Only the young, vital edge sections with fresh roots are reused.
Separate into pieces
Divide the clump with a spade, knife or a firm pull into fist-sized pieces. Each needs roots and growth buds.
Replant at once
Set the divisions in their new spot straight away, at the same depth as before. Do not let the roots dry out, work quickly and in the shade.
Water in and mulch
Water thoroughly after planting and mulch lightly. By winter the pieces root in, next year they shoot up strongly.
Who is divided when
- Divide in autumn (weeks 37 to 42)
Spring and summer bloomers like hostas, daylilies, cranesbill and peonies (carefully). They have finished flowering and still root in before winter.
- Divide in spring (weeks 12 to 16)
Autumn bloomers like asters, stonecrop and most ornamental grasses. This way they start their season at full strength instead of being disturbed just before flowering.
- Every one to three years
Fast-growing perennials like aster and yarrow want dividing more often. Slow ones like peony and bleeding heart prefer to be left in peace.
- Better not divided at all
Taprooted plants like poppy, lupin and monkshood tolerate dividing poorly. You propagate them better from seed or root cuttings.
Spring and summer bloomers in autumn, autumn bloomers in spring. Bare centre out, vital edges replanted, and one perennial becomes many.
The core rule for dividing
Frequently asked questions
When do you divide perennials?
By the flowering rule of thumb: spring and summer bloomers in autumn (weeks 37 to 42), autumn bloomers in early spring. That way you never catch the buds and the plant has the longest recovery before the next bloom.
Why does my perennial go bare in the middle?
Many perennials keep growing outward and die off in the old core. That is normal and the signal to divide: dig up the clump, remove the bare centre and replant the vital edge pieces.
How do I divide a large perennial clump?
Dig it up whole and separate it with a spade, knife or by pulling it apart into fist-sized pieces. Each piece must have its own roots and at least one growth bud. Then replant at once and water in.
Which perennials should not be divided?
Taprooted plants like poppy, lupin, monkshood and bleeding heart tolerate dividing poorly, because their root is injured in the process. You propagate them better from seed or root cuttings.
How often should you divide perennials?
Fast growers like asters and yarrow every one to three years, as soon as they go bare or bloom less. Slow ones like peonies like to be left undisturbed for years and rarely need dividing.
