Propagating flag iris

Steve and Val Bradley explain how to divide these colourful perennials

- Steve & Val

IRIS germanica varieties, sold as bearded or flag irises, are herbaceous perennials with attractive flowers in many colours and horizontal rhizomes (modified stems). They flower best when these stems are on the soil surface, where the sun can bake them in summer to promote the formation of buds for the following year.

New rhizomes

These irises usually only flower once from each section of rhizome and then, as flowering finishes, new rhizomes begin to form from the old ones. These will go on to produce flowering stems for the following year. The new rhizomes are usually large enough to be removed from the parent plant about six weeks after flowering has finished.

Once replanted, this gives the divisions enough time to produce new growth for the following season before they enter their winter dormancy.

Like most herbaceous perennials, it is better to dig up and divide these irises every three to five years. This not only reinvigorates the plants and avoids issues of congestion or disease, but also results in lots of healthy new divisions.

Whether you are propagating the plant or dividing it, always choose the largest fans of leaves with the healthiest rhizomes to keep and grow on. These are usually found like side shoots on the older rhizomes, just behind the old flowering stem.

Clear roots