Taking a cut from the tip of the stem, called the terminal, is a common method of propagation for perennial species. The type of shoot from which the cutting is removed can make a difference in its ability to root. Generally, cuttings taken from the first flush of growth in the spring (basal cuttings) root more easily than tip cuttings taken in midsummer. They may be treated with a rooting hormone containing IBA or NAA. Place cuttings in pots in well-aerated potting mix, water well and cover with clear plastic. Place in a sunny window or under fluorescent lights until rooted.
One can call oneself a bigtime gardener when root cuttings are used for propagation. Useful for a few species, root cuttings are the main means of propagation of plants that do not lend themselves to other routine methods. In this method, the roots of mother plants are dug and washed in late fall. For gardeners with cold frames or hobby greenhouses, plants may be potted up in the fall and stored until the propagation can be done.
Size of the Roots
The size of the roots taken depends on the species. Eryngium and Papaver produce thick fleshy roots, while Phlox paniculata produces thin roots. Generally, 1- to 2-inch-long cuttings are sufficient. Fleshy roots should be placed upright. The end of the cutting nearest the crown should be on top, and the tops should be lightly covered. They may be planted directly into 2- to 3-inch-deep pots and rooted in a cold frame or cool greenhouse. With thick roots, such as those of Anchusa and Polygonum, root pieces may be placed on their side.