The viticella hybrids are the easiest Clematis to grow in both warm temperate and cool climates. The flowers of the viticella hybrids are smaller than some other types of clematis but they make up for this by their sheer profusion over a long period from late spring into early summer in warm temperate climates; they may even rebloom in early autumn. Their flowers also associate well with other garden plants, whereas the larger Clematis blooms sometimes seem like almost artificially unreal prima donnas. Viticella Clematis are robust, long-lived plants; are not subject to clematis wilt; and are easy to prune: simply hack back all the slender twining stems to about 30 cm above ground level in autumn or late winter. The flower shapes vary from cultivar to cultivar: there are nodding bells, open flat blooms, and even fully double forms. The stamens are often coloured in striking contrast to the sepals that make up the inflorescence.
The original species Clematis viticella has nodding, bell-shaped mauve flowers, and hails from Southern Europe. It gave rise to a range of hybrids, many of them raised a century ago by French nurserymen. Favourites include 'Venosa Violacea' (single; white, veined and edged in rich purple); 'Alba Luxurians' (single; white with green tips); 'Etoile Violette' (single; deep purple-violet); 'Betty Corning' (single; bell shaped; pinkish-blue); 'Kermesina' (single; deep red) and 'Purpurea Plena Elegans' (double; dusky reddish-purple).
Give your plant a good start in life with lots of organic matter and ample water in its first two years whilst it establishes its strong root systems; after that it can cope with some dryness. Like all Clematis, the viticella hybrids prefer a well-drained position where their roots are in cool shade but where the stems can grow into sunshine. Flat stones placed around the root area can provide shade, as could a low-growing shrub planted nearby. Annual applications of a balanced fertiliser and organic mulch in late winter will keep the plant flourishing. Protect new shoots from snails and aphids.
The lightweight vines rarely exceed 3 - 4m in height and pruned annually, will never get out of control. They love to scramble through shrubs or small trees: choose a host which is either pruned at the same time as the Clematis - such as a Buddleja, shrubby Salvia, or a rose - or something which doesn't generally require pruning. They can twine through a scrambling rose or other climber on an arch, lattice or veranda post, or behave like a groundcover, weaving themselves across low growing perennials to provide an exotic garland. The darker coloured forms look particularly effective if grown through a silvery leaved host, such as Buddleja 'Lochinch' or Helichrysum petiolare. Purple or blue flowered cultivars are stunning grown through gold or lime leaved plants, such as Duranta 'Sheena's Gold' whilst red forms associate well with purple foliage shrubs such as Berberis.
The best place to find these plants is at a specialist clematis nursery, and these usually have mail order facilities.