The Tree - A Rain Engineer

The pitter patter of rain may induce you to quickly take dry refuge. Nature wants no such escape. Instead, she collects, funnels, and deposits water in some of the most innovative ways. Try a tree as your tutor and you will notice that essentially each tree is a microcosm of an entire watershed, moving water efficiently over its singular, vertically arranged landscape.

Rain drops land on a leaf. Orderly veins or even a slight cupping in most specie's leaves move the molecules effectively until the moisture goes towards stalk or flexible twigs. Or, rather elegant leaf drip tips or edge serrations serve as tipping points to the next leaf below as the gathered weight of the water spills again and again under the force of gravity. Even needles concentrate water and send it on its way to twigs. You are not likely to feel the initial rain drops under a tree, but only the larger concentrated globs that now split and splatter under the canopy.

Trace the next path of a drop from its leafy headwaters towards the twigs and larger branches. Most trees have branches that ascend or have a rather sinewy pattern which guides the direction of the liquid downward. You could imagine this as the waterways of first order, second order, and so on as the sky's liquid coalesces into streams and rivulets. Check out the evidence from a native sycamore in a city setting. Many times, the dark particulate matter it captures in an urban environment gets rearranged and deposited under the large whitish branches. Sometimes you can yet trace the water tracks when dry.

Dark V-shaped lines of deposited particulate matter on the underside of a sycamore tree limb show the pattern in which water moves along tree limbs toward the trunk (image credit: Julianne Schieffer, Penn State Extension).

Of course, the trunk connects all those branchy waterway networks. Diamond shaped funnels or ridges of bark pattern (much like mountains and valleys) guide the flow drip by drip until you have a larger river going down the trunk, always following a path of least resistance. Notice that the bark on the trunk does not wet unless there is a driving wind. Ironically, it tends to resist water. The bark sheds or delivers that rain made cargo to the estuary or base of the tree. There the highest concentrations of roots go to work absorbing. Perfect placement!

This efficiency especially comes into play when a light sprinkle may not even dampen the soil. By keeping the collected water in its canopy instead of letting the roots pick it up from the soil, the tree again concentrates and gathers the liquid until by weight and mass it make its way to the roots. The tree may expend less energy by design instead of actively using root growth and other processes to gain access to this water.

My hope is that you too will want to witness and experience the path the sky's liquid takes across a tree's surface. Let a tree reveal its engineering marvel of moving water during a deluge, and you may never feel the need to make that mad dash to stay dry again!