Trim your beards

They’ve flowered their socks off for you this summer so to keep the displays coming year on year, now is a good time to step in and split up your bearded irises. Don’t feel obliged to complete this task annually – every three or four years is fine – but do so to maintain plant vigour and flowering ability, and complete it before the end of September. These varieties of iris (often sold as selections of Iris germanica) are so-called because of their fluffy, hair-like filaments on the lower petals. They form a fleshy rhizome which need to be partly exposed to the sun in order to ripen and bloom well.

Dividing Iris germanica - lifting the plant - © Thomas Alamy/GAP Photos

Dividing Iris germanica – lifting the plant – © Thomas Alamy/GAP Photos

Trim over your iris clumps to remove old flower spikes and faded brown foliage, then reduce the height of the remaining leaves to 15cm above soil level.

Dividing iris with a garden fork - © Elke Borkowski/GAP Photos

Dividing iris with a garden fork – © Elke Borkowski/GAP Photos

Now you have a clear view of the rhizomes, step in with a spade or fork and lift up any congested clumps. The objective is to discard the older parts and keep the younger, more productive sections.

Trimming Iris roots at Woottens Nursery in Suffolk - © Juliette Wade/GAP Photos

Trimming Iris roots at Woottens Nursery in Suffolk – © Juliette Wade/GAP Photos

Throw away any sections of rhizome that are small, weak or withered, and retain those that have a strong cluster of leaves and thick, plump stems. Trim any over-long roots.

Planting of divided clumps of Irises as the same depth as before - © Elke Borkowski/GAP Photos

Planting of divided clumps of Irises as the same depth as before – © Elke Borkowski/GAP Photos

Replant the young rhizomes at their original depth. Don’t bury them too deeply in the soil – you want to anchor the section in place with the roots, but have the upper half of the rhizome exposed to the sunlight. Water in well.