Dividing clumps of perennials

September and October is the ideal time of year to do a little maintenance work on your hardy perennials, and particularly to divide overgrown clumps of plants. The idea is to keep the vigorous bits, usually on the outside of the plant, and discard the weak or even dead bits in the middle. It’s not an especially difficult job, and it means that your plants will grow better next year. What’s more, you’ll have several plants instead of just one, so if you don’t have room for the new plants, you can give them away to family and friends, and make yourself popular! So what do you need to do?

1)     Decide if dividing is necessary for that particular clump

You only need to divide perennials every three to four years, and not all of them need or indeed want dividing, so do check whether it’s actually necessary before you start. If a clump of your chosen perennial looks like it’s getting very overcrowded, or all the growth seems to be around the outside, with a space developing at the centre of the plant, dividing is probably a good idea. Otherwise, it’s probably best to leave it for a while.

2)     Dig up your clump

Make sure you take the whole rootball, which can be surprisingly big for a mature perennial. If it needs dividing, the rootball will probably be at least a fork’s depth, and maybe more around.

3)     Tease the roots apart

Use your hands if possible, as this will do least damage to the roots. If the roots are too tangled, then use two garden forks. Place them back to back in the centre of the clump, and ease them gently apart, taking the roots with them. Any thick or tough roots that refuse to separate can be cut with a sharp knife.

4)     Replant

Remove any dead or tired parts from the plant, and get yourself two or three smaller clumps of really vigorous looking shoot and root combinations. You can replant one of those clumps in the same hole, although it’s probably a good idea to add some organic matter to the base, maybe home-made compost, or some new topsoil (click here if you need to buy topsoil), just to give the plant a bit of a boost. Firm the plant in, and water well. If it doesn’t rain for a few days, remember to keep it watered until the roots have re-established.

Your other healthy clumps of plant can either be replanted elsewhere in the garden, or you can pot them up temporarily, using either good quality topsoil or potting compost, and keep them to give to friends, use for plant sales, or to fill gaps in your garden next year.