Periploca is an Old World genus containing 9 species of perennial climbing leafy vines. Stems, becoming woody with age, bear opposite oval leaves and are without tendrils.
Several species in this genus are listed as invasive weeds and are best cultivated in large pots with a climbing frame, where they can be kept under control. Place the pot on a paving stone or the plant may send a root down through the bottom of the pot and establish itself in the ground.
Periploca graeca Linnaeus 1753 (Silk Vine, Climbing Dog's Bane)
native in southern Europe to Asia Minor. The smooth stems are frost hardy and will grow at least 30 ft long, although the large ovate leaves are shed in the Autumn. Stems are initially green and develop brown bark as they mature. The attractive flowers are dark purple, markedly hairy and appear in mid to late Summer. Their scent is considered attractive by some people and unpleasant by others. As with other Asclepiadaceae the seeds within the poisonous yellow fruits have a silken parachute which assists dispersal by the wind. Sap and fruit contain cardiotoxic steroids (cardenolides), some of which have shown activity as anti-cancer agents. In Eastern countries, the acrid sap is used as a wolf poison and presumably toxic to other animals.
Periploca graeca grows in any fertile soil in a sunny position and is perhaps too undemanding as it is liable to outgrow its welcome if planted in the ground. It is easily propagated from cuttings of half-ripe wood or from seeds. Cuttings root easily in a glass of water before potting on. Best grown in a planter with a tall climbing frame, stood on a paving stone to stop the roots invading the ground through the bottom of the pot.