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Clematis can be propagated using several methods. The best method to use will depend on the species or kind that is being propagated. Seed is a good way to start new plants as long as it is only collected from a true species. Cultivars or named varieties will not come true from seed. Collect fresh, ripe seed and sow directly in the garden in autumn, or sow the seed in shallow pots filled with sandy soil in February in a cool greenhouse. To ensure even germination, the seed must go through a cold period known as stratification. This will occur naturally if the seeds are sown directly in the garden in autumn. Otherwise, store them at a temperature as close as possible to 39°F for approximately 3 months. After this cooling period, sow them in a moist media recommended for seeds and maintain them at a temperature near 70°F until they germinate. Be sure they have bright light so they will not become spindly. Once they are large enough to handle, transplant to 4 inch pots.
Most clematis species and their cultivars can be propagated easily from leaf-bud cuttings. Collect softwood cuttings from spring to mid-summer and semi-ripe cuttings from mid- to late summer (July or August) from the current seasons growth. Semi-ripe cuttings are not so demanding when it comes to providing a humid rooting environment. Soft-wood cuttings will dry out much quicker than semi-ripe cuttings, but both must not be allowed to dry out.
These cuttings are made from 2 inch long pieces of stem. To make the cuttings, cut on a slight angle directly above a node or joint (where the leaves emerge from the stem) being sure there is a strong, healthy bud in each leaf axil (the angle between the stem and the leaf petiole (leaf stem) of that cutting. Always use a sharp knife or pruners when taking cuttings. There will be two buds because the clematis has opposite leaves (one leaf grows directly opposite the other on the stem) and a new bud is formed in each of these leaf axils. It is important that these buds are strong and healthy and not damaged when the cutting is taken, otherwise, the cutting may fail to grow. The nest step is to cut the stem off about 2 inches below these leaves and buds. Roots will form anywhere along this stem. This is known as an internodal cutting because roots will form anywhere on the stem between the nodes or joints. A nodal cutting is used for plants that do not root readily along the stem. Nodal cuttings are made by cutting straight across the stem, directly under a node where roots will form more readily. Clematis species with large leaves should have the leaf on one side of the stem removed completely, and the remaining leaves on the opposite side should be cut in half with a sharp sciccors. This will reduce moisture loss of the cutting through transpiration. The cuttings can then be dipped in a gel or powder rooting hormone and inserted in a moist medium recommended for starting cuttings. Place the cuttings in bright light (not direct sun), provide a bottom heat of 55 - 60°F and place a clear plastic bag over the cuttings to keep them close (warm and humid). Once they are well rooted, they can be repotted in 4 inch pots, grown on, and then hardened off gradually and planted outside in their permanent location.
Clematis can also be propagated in the spring by simply dividing large plants. Each division or piece should be fairly well rooted. A few species can also be propagated by layering. This is done by choosing a healthy stem, making a slight cut on the underside of the stem near each node, laying the stem on the soil and burying the stem with soil. The stem is then pinned down to keep it in contact with the soil. The new plants are usually well rooted by the following year. Grafting clematis is probably best left to the experts.
