The following series of columns entitled ‘Soil to Sky’ are an examination of five different facets of environment, structure, and life that are instrumental to trees in our forests and landscapes. Trees are instrumental to our wellbeing, both individually and collectively as a society. Healthy urban forests and natural areas are the responsibility of professional arborists, policy-makers, volunteers and individuals, among others. We will be sharing our enthusiasm with you in weekly installments and encourage you to become tree stewards, heralding forth the future of healthy trees. See the previous columns here: Soil, Roots, Stem.
Leaves and Branches by Alyssa Vinson
Oh, the many patterned dynamic shapes of leaves that occupy the reaching limbs to congress, convert and control the air, the sun, and the influence of canopied emerald reaches. Ovate, pinnate, palmate, petiolate are just some of the names that help confer the diversity of form. Held up to the light from petiole, up the midrib and see vascular ingenuity reaching across lamina to engage the photosynthetic consumption of solar energy. Whether leaf or needle, deciduous or evergreen, each is a product of need, desire, ingenuity, and efficiency. A particular adaptation for a particular purpose based on evolutionary need.
Alternating, whirling, or encapsulating leaves traipse their way, delicately emerging from bud at node to perform the function of magical transformation, sunlight to sugar. Do they reach, grasping in unison for the wave that traverses stellar geography? Minutely hidden within their uniform cellular walls, the factories in chloroplasts rely on nutrients transported upward, plus solar energy to create sugars. These sugars are then transported downward for storage and use or transported to neighboring trees. Shapes as varied as the vast numbers of stars, smooth margined, undulate, lanceolate, cordate, belie the evolved placement within the ecosystem. Those leaves seeking sun in the understory are large and many lobed or held aloft and pinnacled, some leaves spiky to thwart the herbivores, shapes follow function and circumstance.
Held brightly aloft, leaves are lifted to the sun by the skeletal and exuberant branches. Pathways of branches when viewed from above mirror rivers in their fractal patterns, as they negotiate the reach for maximal light. Encased in corners, joints, the ability to protect from damage, disease, and pests. When cut or damaged, branches will encase the wound preventing harm from travelling through the entire tree. Auxins at the tips of branches hold the key to new growth, and nodes, allowing new branches to emerge from wounds of old. When draped in maturity, branches form a safe layered, nested, universe within the canopy. Highways for mammals, fiefdoms for birds, branches encase kingdoms or provide shelter for those animals travelling vast distances. Tiny and mighty insects abound, and the epiphytes find their homes nestled amid the branches. Each canopy an ecosystem, with niches to fill and balances to be struck.
Within the arched dome of the canopy, our own longing for heights and the unique perspective of our world from aloft. Treehouses, ladders, ropes, and swings, all the journeying equipment of childhood. How many fingers ached to reach that next highest branch, only to slip and meet with a scraped shin and a bruised ego? Once climbed, the view from the canopy is one unmatched by a foundation of terra firma, an opportunity to expand the perspective of our human limitations and feel the drift and sway of the winds play on arboreal perch.
Once dutifully articulated in the arching pattern between horizons, leaves will find their way between the twisting breezeways from branch to soil to replenish the newly budding factories. In a final flourish, clothed in crimson or burnt umber (if luck should have it in the northern climes), leaves give themselves in preparation for the continuance of the whole. No fanfare other than the glistening sun, farewell to the individual as we mark the path downward on autumnal wind. The leaf then, should be left in reverence upon the surface of the soil or kindly entombed in the warmth of a compost pile.
Within the twisting branches holding their (al)chemical miracles (sunlight to sugar!). We are greeted with an opportunity as stewards of our community trees. To welcome the sun with well-structured branches, avoid pruning downfalls such as ‘lion’s tailing’ or ‘flush-cutting’ that weaken, and stress the tree. Leaves give signals to the overall health of the tree, you can watch for signs of stress or decline by gazing periodically into the mesmerizing canopy and noting any changes in color, shape, or sudden losses of leaves. In tree stewardship, careful observation and deliberate mindfulness can lead to a healthy and long-lived community forest.