It’s important to divide your bearded irises every few years to keep them floriferous and healthy, and to make new plants.
The traditional technique is to dig up the iris six weeks after flowering, divide and replant. However some iris growers, such as Doddington Hall in Lincolnshire, achieve just as good results by dividing the iris while it’s still in the ground.
Whichever method you choose, it’s important to divide immediately after flowering (at the end of July-mid August) because plants begin making new flower buds for next year, from late August.
STEP BY STEP
1) Cut the main clump into pieces 6in (15cm) long. Ensure each has a healthy fan of leaves
2) Discard any small or rotten pieces. Trim the roots of the healthy ones by about a third
3) Next trim the fan of leaves by half: this prevents windrock and reduces moisture loss
4) Replant each about 1ft (30cm) apart – at soil surface on heavy soils, below on sandy ones