How to divide perennials

Video by GrowVeg. This guide draws on "How To Divide Perennials — Expand Your Garden for Free" from the GrowVeg channel, one of the UK’s most trusted gardening YouTube channels with over a million subscribers. Their walk-through of the two-forks method is particularly clear, and the advice on which sections to keep and which to compost is exactly the kind of practical detail that makes this job much easier the first time you tackle it.

1. Know when to divide

The timing depends on when the plant flowers. As a general rule: divide summer and autumn-flowering perennials in spring, when they are just showing new growth but have not put up significant top growth yet. Divide spring-flowering perennials in early autumn, after flowering has finished.

Hostas, daylilies, achillea, rudbeckia, echinacea, phlox, and most ornamental grasses all respond well to dividing. Avoid dividing things like hellebores, which resent disturbance, or plants that have just been put in — give them at least a full growing season first.

2. Prepare the new planting spots first

Do the digging and soil improvement before you lift the plant, not after. Once a clump is out of the ground, you want to replant quickly so the roots do not dry out. Dig over the new spots, work in some garden compost if the soil is thin, and have a watering can ready.

If you are replanting divisions back into the same border, dig in some fresh compost to replenish what was there — perennials exhaust the soil around them over several years.

3. Dig up the whole clump

Push a fork in around the outside of the clump at a slight angle and lever the whole rootball out in one go. Work around all sides before trying to lift — forcing a fork under a clump that is still anchored at the back will snap roots you want to keep.

Lift the clump onto a piece of old tarpaulin or a flat surface. Shake or knock off excess soil so you can see what you are working with. Most established perennials will have a dense, interlocking rootball that needs some encouragement to separate.

4. Split the clump into sections

The two-forks method works well for most clumps: push two garden forks back to back through the centre of the rootball, then lever the handles apart. The roots tear rather than cut, which is fine — the plant does not mind. Work the clump into sections roughly the size of your fist or slightly larger.

For clumps with woody centres or tough, fibrous roots, a sharp spade or even a pruning knife may be needed. The key rule: discard the old woody centre of the clump, which flowers poorly. Keep the young, healthy outer sections with good roots and fresh growth buds.

5. Replant the healthy divisions promptly

Set each division at the same depth it was growing before — you can usually see the soil mark on the stems as a guide. Firm the soil around the roots to eliminate air pockets, but do not compact it hard. Space divisions a bit further apart than you think is needed — they will fill in quickly.

For spare divisions you have no space for immediately, heel them in temporarily in a shaded spot or pot them up. Many gardeners find the surplus divisions are more than welcome with neighbours — perennials are worth money at a garden centre.

6. Water in well and mulch

Give every replanted division a thorough watering immediately, even if rain is forecast. The roots need good soil contact to start recovering. Apply a mulch of compost or bark chippings around each plant — not touching the stems — to retain moisture while they establish.

Keep an eye on them through the first few weeks after replanting, particularly in dry weather. Divided plants look a little sorry for themselves at first. By the following season they will be fuller, healthier, and usually flowering much better than they were before.

7. Feed if needed

Once the divisions are showing strong new growth, a balanced general fertiliser or a handful of slow-release granules will help them hit their stride. Avoid feeding immediately after planting — the roots need to settle first. About two to three weeks after replanting is about right.

When to call a handyman

Richard can help if you have a large border that needs a full renovation — lifting, dividing, and replanting a whole bed at once is heavy work and takes a full day on a mature garden. He can also help with the preparation: improving the soil, clearing persistent weeds before replanting, or bringing in fresh topsoil or compost.