Cuttings can be taken now and up to mid September perhaps even later

. Take a 6-8 inch cutting of a non flowering stem. Cut just below a leaf joint . Remove lower leaves and I cut half off the the leaves I leave on as big leafed cuttings lose too much water.

Place the cutting in a mix of 3 parts potting compost and one part horticultural sand and place in a shady spot (I use a coldframe with translucent white polythene )

You can dip the cut end of the cutting in rooting compound but I don't bother.

If you're not used to taking cuttings you might find this sequence of photos I produced on the subject with text useful

http://www.flickr.com/photos/31559373@N00/725769578/