How do rainforest plants live in mid-air, from orchids to strangler figs?

In a rainforest the light is high up and the soil is down below, so some plants simply skip the soil. Epiphytes grow on the surface of another plant, usually a tree, and take their water and minerals from the air, the rain and the debris that collects around them. They are not parasites: an epiphyte uses its host for physical support only and draws no nourishment from it. In the tropics they include many orchids, ferns, cacti and bromeliads, and a rainforest tree's epiphytes may weigh several tonnes.

Life up there has an advantage: more light than on the dim ground, and herbivores may be more active down there. But it takes ingenuity to get nutrients without roots in the soil. Epiphytes catch them from fog, dew, rain and mist, or from nutrients that rooted plants release through decomposition or leaching. Some of them hold water in the canopy, and certain frogs and arthropods live in those little reservoirs.

Strangler figs play a longer game. Their seeds, often carried by birds, germinate in a crevice high on another tree. The seedling starts life as an epiphyte, then sends its roots down and around the host while its shoots race upward toward the sun. This habit is an adaptation to dark forests where competition for light is intense. If the host dies, the fig may stand alone as a hollow columnar tree.

Lianas take a third route. They are woody vines that root in the ground and climb trees to reach the sunlight, and they cost their hosts dearly: trees with lianas have twice the probability of dying. Yet lianas also form rope bridges through the canopy for ants, sloths, monkeys and lemurs. And if you have an orchid on your windowsill, you already know that epiphytes make good houseplants.