As you dig around the plant, try to disturb it as little as possible. Look for roots that are - inch in diameter. Root cuttings grow best in warm soil, so if you collect them during the winter bury them in moist sand and keep them at 40 degrees F until spring. To plant the cuttings, dig a hole and place a cutting in it horizontally. Root cuttings can also be planted in trays or pots, and then planted out after they develop leaves and the root system fills the pot.
Many herbaceous plants have underground stems called rhizomes.
These can be used to propagate plants in a manner similar to root cuttings. Again, because this technique can harm the parent plant, it should not be used in a natural area unless it is slated for bulldozing. With your hands or a hand trowel, carefully dig around the plant to locate the rhizomes. Once located, severe the rhizome from the parent plant and dig the segment up. Immediately plant the rhizome sections horizontally in pots, flats, or on-site.