Why have my bearded iris failed to bloom this season?
Gerry Stephenson, by email
Stefan says: I’m amazed they’ve kept flowering for 15-20 years in the same border because bearded irises multiply their stout, fleshy rhizomes at a remarkable rate and I usually advise dividing them every three or four years.
I suggest you start afresh next spring. Dig up the entire bed and place the rhizomes to one side. Dig the bed thoroughly and remove all perennial weeds and apply an overall dressing of bone meal. Pull away the young, vigorous pieces from around the periphery of the iris clumps and discard the old, tough and moribund material towards the centre. Cut down the mass of leaves by about two thirds and plant the new pieces about 20cm (8in) apart by making shallow hollows in the soil with your hands, then carefully firm a mixture of soil and compost over the fibrous roots and around the rhizomes, but be careful not to bury them deeply.