The forest that drinks from cloud

The laurisilva is a relic. Twenty million years ago forests of this kind covered southern Europe; today they survive in fragments on Atlantic islands where cloud and mild air keep the humidity high enough. Madeira holds the largest remaining area, and it is protected as a UNESCO World Heritage site.

What makes it work is not rain but interception. Moisture carried in cloud condenses on leaves, moss and bark, and reaches the ground slowly — a form of precipitation that never appears in a rainfall figure. The forest effectively harvests its own water.

For garden design this is the useful lesson. Under a canopy, the limiting factor is rarely irrigation; it is drainage and air movement. Ground that stays wet and still will rot roots faster than dry ground will starve them.

It also sets a limit. A private garden cannot reproduce a forest that needs continuous canopy and decades of leaf litter. What it can borrow is the structure: tall canopy, dense understorey, ferns instead of lawn, and a ground plane that is never bare.