Clematis is a group of mostly vigorous, woody, climbing vines with showy flowers. For pruning purposes, all Clematis are grouped into three groups with specific pruning requirements.
Group 1: Spring bloomers, bloom early in the year, and bloom on the previous year's growth. These should be pruned lightly right after flowering, if at all.
Group 1 includes the Clematis species: alpina, armandii, cirrhosa, macropetala and montana.
Group 2: Early to mid-season flowering cultivars and re-bloomers, these bloom in early summer on the previous year's growth, and then again on new growth. Prune in late winter or early spring, remove dead and weak shoots. Cut back the remaining shoots to 6-9 inches above well developed buds. Prune lightly.
Group 2 includes 'Blue Explosion', 'Gillian Blades', 'Niobe', 'Love Jewelry', 'Multi Blue, 'Diana's Delight', 'Cezanne' and 'Picardy'.
Group 3: Late flowering cultivars, these are summer blooming clematis which bloom on new growth beginning in midsummer and then again on new shoots in the fall. These should be pruned in late winter or early spring, and all shoots should be cut back to the previous year's wood above the base of the plant. Leave at least two strong sets of buds on each stem, while pruning severely.
Group 3 includes fargesiodes, Huldine, Jackmannii, Moonfleet, 'Betty Corning', Princess Diana and viticella.