Some herbaceous perennials are best propagated just after flowering. This includes the familiar bearded iris, whose chunky rhizomes lie flat on the soil. Have a look and you will see that some of the rhizomes bear young fans of leaves at their ends, but no flowers. Take an old carving knife and cut cleanly through the tissue to leave a length of rhizome and a fan of leaves. Use a fork to tease the severed joint gently from the soil, dust the cut surfaces with sulphur and press the new piece into cultivated soil so that it’s barely covered.