Clematis may be divided into three main groups according to their flowering time and habit. The first group includes early-flowering species and their cultivars and Alpina, Macropetala and Montana groups, which flower directly from the previous season’s ripened stems. The second group includes early, large-flowered cultivars which bloom on short, current season’s stems that arise from the previous season’s ripe wood. The third group includes late-flowering species, late, large-flowered cultivars and herbaceous types which flower on the current season’s growth.
When planting a clematis make sure you plant it about 5 cm deeper than normal to encourage basal buds to develop below soil level. So, if by any chance the stems are damaged the plant will be able to grow again from below soil level. Keep newly planted specimens well watered until established and mulch climbing and herbaceous species annually in spring with garden compost or well-rotted manure. The evergreens clematis and species such as Clematis tangutica and Clematis orientalis should not be grown in soil that that lies wet during the winter as they have fine, fibrous root systems that quickly rot.
If you want to propagate clematis you can sow seeds in autumn and overwinter in a cold greenhouse or frame. Cultivars do not come true from seeds so to propagate them use softwood or semi-ripe cuttings taken in spring or by layering. For herbaceous types use division or basal cuttings. Softwood or semi-ripe cuttings are taken in spring just above a node, then trim the stem to 2.5-5 cm below node. Remove one of the pair of leaves 1 cm away from the node then reduce the remaining leaf area by half and cut the stem above the node back to approx 1 cm. Treat the base with hormone rooting powder and root in a closed propagating case with bottom heat. Harden off the new plants gradually before planting them out in spring.