Asked by: Nick Davies, by email
Climbing is a parasitic behaviour that saves a plant the effort of making a strong trunk or stems of its own. There are several distinct strategies. Ivy uses specialised roots that work into tiny fissures in tree bark or a wall, while clematis has leafstalks that twist around the stems of another plant to anchor it as it grows. Cucumber plants have tendrils that wrap around another stem and then pull the plant up by coiling up the tendrils.
Climbing plants normally start by creeping along the floor until they reach a stem. Although the point of climbing is to escape the shade, some tropical climbers begin by growing away from the light, because this makes them more likely to reach a tree trunk. Once they touch something, the physical contact triggers chemical changes that stimulate the climbing behaviour and the plant begins to grow against the direction of gravity.