The Architecture of Trees
"Trees appear to be too complicated if we don't have the key. I will give you the key to trees," Francis Hallé
Renowned botanists, Francis Hallé and Peter Del Tredici, came to the University of Virginia (UVA) to teach landscape architecture students about the architecture of trees. Hallé is a professor emeritus at the University of Montpellier II, where he studies tropical rainforests. UVA landscape architecture chair Teresa Gali-Izard, International ASLA, introduced him as a botanist, biologist, artist, and poet. Del Tredici is a botanist and research scientist at Harvard's Arnold Arboretum and professor at Harvard's Graduate School of Design. His research includes wild urban plants and plant morphology.
As the first workshop on Saturday afternoon began, Hallé defined plant architecture through 22 known models of tree growth and morphology. We learned how certain logic plays out in the growth of a tree. The diagrammatic quality of his drawings demonstrated growth habits and the potential for reiteration, which refers to a tree's response to damage with the redirection of nutrients. Hallé developed concepts of reiteration and tree adaptability, explaining how these capabilities formed out of tree evolution.
Hallé insists the key to understanding trees lies in the difference between unitarian and modular models. Unitarian trees have ancient methods of reproduction – they are consistent and symmetrical throughout their entire life. When a unitarian tree is pruned, the plant lacks the means to reproduce from the cut. Modular trees work in a more complex way – as the tree grows the branches create a dendritic pattern. When a modular tree is pruned, the tree responds through reiteration. A modular tree is adaptable because it can reproduce more modules of the original tree form throughout the canopy.
Full of ideas on how to draw, plant, understand trees, students and faculty set out in the rain to draw and study trees on the grounds of UVA. We looked at specific instances of reiteration in action: tree collars, water sprouts, fluid tree growth dynamics, and grafting.
The following morning we walked to the side of Carter's Mountain along the Monticello Trail. We lingered with certain plants: eastern white pine, devil's walking stick, tulip poplar, eastern redbud, and an oak. We encountered visible reiteration in the forest surrounding Monticello.
"Wood is plastic," Francis Hallé; "Trees have fluid dynamics," Peter Del Tredici
Peter Del Tredici then discussed biological functions in architectural models of trees. Discussion of meristems (the tissue in plants enabling regenerative growth) and the fluid dynamics of trees informed Del Tredici's examples of tree adaptability. Images of trees growing through chain link fences, massive tropical tree buttresses, or trees converting dead internal cambium into soil for new growth all demonstrated the ability of trees to change and succeed within taxing environments.
Our final group workshop gathered into a large informal critique of the work UVA landscape architecture students completed as part of courses on planted form and function. The work included axonometric drawings of plant communities in Virginia, specific and general examinations of plant architecture, and some experiments in representing representation types of planted forms (hedge, alleé, windbreak). While we discussed methods of drawing plant architecture with Hallé and Del Tredici, other questions at the intersection of botany, design, and preservation arose.
As landscape architects and students, we know tree maintenance is a critical part of design. Though Hallé insists cutting a limb of a tree is "like cutting the leg of your dog," we pondered the reasons for pruning a tree. Gali-Izard and UVA professor Julie Bargmann wondered about the role of the landscape architect's role in pruning: "I love trees. I want to touch them," and "Why can't I be the lightning strike?"
We talked about the cultural implications of cutting a tree, as well as pollarding, hedging, or training trees. Though no ethical conclusion emerged from the conversation, Hallé said it well, "to prune a tree you must have a very strong reason."
This guest post is by Hannah Barefoot, Master's of Landscape Architecture candidate, University of Virginia