Glossary

Dividing herbaceous perennials is a key job for gardeners. It helps to keep plants healthy, keeps them flowering freely, and stops older plants becoming compacted and bare. At the same time it also gives you more plants for nothing! 

When’s the best time to divide?

Basically, spring- and summer-flowering plants are best divided in autumn, autumn-flowering plants in spring. In each case this gives the plants enough time to put on new growth before their next flowering period. If you’re not sure it’s best to go for spring division – that’s generally the safer option.

These perennials are typically divided in autumn:
Autumn division works very well for peony, iris and daylilies. The ground is still warm and often moist and the plants have already stopped growing – perfect conditions for stress-free division.

Perennials that prefer spring division:
Ornamental grasses, phlox, hostas and autumn anemones are sensitive to wet winter conditions and late cold snaps. Dividing them in spring gives them more time to form strong new roots.

How to do it:

Carefully dig out the plant. Then separate the root ball into several pieces – with your hands, with a sharp knife or with a spade. Each piece should have healthy roots and at least one shoot tip for new growth. After this replant the divisions in well-prepared soil, firm them in and water well.

Tip: Make sure you replant your new plants at the right depth – for peonies and iris this is crucial for them to flower well.