Plumbago can be rooted from stem or root cuttings. Unless you will be rooting them indoors, make the cuttings in fall or spring so the rootings benefit from mild temperatures while they become established.
Cuttings should be 3 to 4 inches long, taken just below a leaf node, recommends Andromeda Botanic Gardens. Strip the leaves from the bottom half of the plumbago cutting. Dip the stripped half in water, then in rooting hormone, if available. Use a pencil to make a depression in the soil where you will plant your cutting. Place the cutting and firm the soil around it.
The University of Florida recommends root cuttings for propagating plumbago. Take cuttings from the mature root (1/4- to 1/2-inch diameter) of a two- to three-year-old plumbago in late winter or early spring, says the University of Florida IFAS Extension. Bury 2- to 6-inch-long cuttings horizontally under 1/2 inch of rooting medium.
Keep plumbago cuttings out of direct sunlight but in a bright place until they've rooted. Keep the soil evenly moist. Covering the cuttings with a clear plastic covering helps conserve moisture and prevents wind damage.