Why not divide each clump , taking a small part of each herb that you use. Carefully scutinise it for mint "spears " and then pot it up, placing to one side. Select some mint specimens and plant in a clay pot, also place to one side. Sustain these until they are growing vigorously. Then dig out the old block of herbs remaining, cart away to an odd corner. Create the new herb garden in the old spot and supply plenty of good compost. Plant out your saved stock, and plunge the mints in the clay pot(s) to sit rims flush to the surface. If you discover any have failed to establish, return to the discarded pile and locate another . If you have space, collect new plants to your taste. A good "haircut" of many herbs will serve to rejuvinate and repair leggy examples.
