Traveller's-joy
Clematis is a cosmopolitan, temperate northern hemisphere genus comprising 200-300 species. Most species are woody climbers, although some are non-climbing shrubs. Biomechanical studies show that the stems of traveller's-joy change their properties with age. Young stems are self-supporting, but they soon lose this ability and relying on the structures over which they clamber for support. The generic name is derived from an ancient Greek word used to describe climbing plants.
The native range of Clematis vitalba extends through Europe into North Africa and western Asia. It is native to the southern part of Britain but has been widely introduced and naturalised as far north as central Scotland. It is also widely naturalised globally, in temperate regions, where is may become a serious invasive species. For example, in New Zealand Clematis vitalba causes structural changes to forest canopies and facilitates the establishment of other species.
Clematis vitalba is a deciduous scrambler with stems that may extend up to thirty metres, covering large areas of hedgerows, walls, forests, sand dunes and railway banks. It is most obvious in mid-summer, when the plant is covered in dense clusters of creamy-white, fragrant flowers, and in the autumn and early winter, when these are replaced by pompoms of grey-white, feathery fruits. The appearance of the fruit-heads gives the species one of its other common names, old man's beard. The name 'travellers-joy' was coined by the sixteenth-century English herbalist John Gerard because of the plant's habit of 'decking and adorning waies and hedges, where people trauell, … The plants have no vse in Phisicke as yet found out, but are esteemed onely for pleasure'.
Clematis vitalba flowers are primarily pollinated by hoverflies, where the reward is nectar, which is produced by the flattened filaments of the stamens. The dry, wild-dispersed fruit, which contains a single seed, has an elongated, feathery style. Experimental results show that Clematis vitalba is capable of both inbreeding and outbreeding.
The leaves of Clematis vitalba are arranged in an opposite fashion on ridged stems. Each leaf comprises three to five leaflets. Charles Darwin, who was fascinated by climbing plants, considered Clematis species to be leaf climbers. That is, they use the stalks of the leaves or the leaflets to climb. Traveller's-joy was one of six Clematis species whose climbing behaviour he studied in detail. He observed that the slightest pressure from another structure was enough for the petiole to start bending around it.
Further reading
Isnard S and Silk WS 2009. Moving with climbing plants from Charles Darwin's time into the 21st century. American Journal of Botany 96: 1205-1221.
Isnard S et al. 2003. Mechanical architecture and development in Clematis: implications for canalised evolution of growth forms. New Phytologist 158: 543-559.
Redmond, CM and Stout JC 2018. Breeding system and pollination ecology of a potentially invasive alien Clematis vitalba L. in Ireland. Journal of Plant Ecology 11: 56-63.
Stephen Harris