Advice
RHS Help & Advice
Dividing perennials
Most perennials benefit from division every two to three or so years to maintain health and vigour, as well as to propagate new plants.
Timing
Plants can be divided successfully at almost any time if kept well-watered afterwards. However, division is usually most successful while plants aren’t in active growth. Divide summer-flowering plants in spring or autumn, and spring-flowering plants in summer after flowering.
Soil preparation
Work bulky organic matter, such as garden compost or well-rotted manure, into the planting hole. If re-planting into the same site then also add a slow-release fertiliser such as bonemeal.
Lifting and dividing plants
Some plants, such as Ajuga (bugle) produce individual plantlets which can simply be teased out and re-planted. Most however require lifting and dividing.
Lift plants gently with a garden fork, working away from the crown centre to limit root damage. Wash off excess soil so that roots are clearly visible.
Small, fibrous-rooted plants such as Heuchera or Epimedium (see left) can be pulled apart. Larger fibrous-rooted perennials such as Hemerocallis require two garden forks inserted into the crown back-to-back (see above). Lever the forks to loosen the root mass.
Plants with woody crowns (e.g. Helleborus) or fleshy roots (e.g. Delphinium) require cutting with a spade or knife. Aim to produce clumps containing three to five shoots.
Aftercare
Plant divisions as soon as possible and water them in well. Alternatively pot up individually to build up size, overwintering pots in a frost-free environment.
Further information
Current research from Wisley into composting and mulches
Search the online RHS Plant Finder for suppliers of perennials or search for Award of Garden Merit plants with the Award Plants database
Useful links