Fill a small pot with a good quality, well-drained growing medium. Use a combination of sphagnum moss, perlite, sand and vermiculite, as recommended by the North Dakota State University Extension Service.
Take two- to six-inch cuttings from the roots of the parent plant with a sharp spade. Tie the cuttings together in a bunch. Store them in moist peat moss or sawdust at 40 degrees F for about three weeks. Take two-inch sections if roots are thin. Recommended time to take root cuttings is during the dormant season.
Plant cuttings about five inches deep in prepared pot. Do not plant too deeply as this leads to poor growth due to insufficient oxygen. Keep soil moist but not wet.
Transplant when new plants have developed from the cuttings. It takes about a year for healthy, strong plants to develop from root cuttings.