Now is the right time to do this. Use a gritty compost and use a small pot or seed tray if you want lots of new plants. Take 2-3 inch cuttings from non-flowering shoots. Trim off the lower few leaves and dip in hormone rooting powder. Insert cuttings about an inch apart, water in and keep in a sheltered place in the greenhouse or on a windowsill. They should root in a few weeks, then pot them on or leave this til spring. Grow the cuttings into decent little plants before planting out next year.