Trees are a natural choice for creating the framework of a garden, marking the perimeter, serving as focal points or a kind of sculptural art, and providing shade and privacy for intimate areas within the larger space. The hardscape of a garden plays a similar role, outlining boundaries and creating interior lines with pathways and patios, walls and fences. But as living structures, trees add elements of change and surprise. If properly sited, they flourish as they pass through the seasons and influence the selection and health of surrounding shrubs and perennials.
When planning a garden, first choose the trees.
From a design perspective, trees anchor the garden with the color and shape, texture and scent around which the rest of the design evolves. In his wonderfully succinct “Landsca
pe Design Principles for Residential Gardens,” Rob Steiner recommends planting big to small, starting with trees, the sixth of eight rules for effective garden design.1
From a practical perspective, trees increase property values by shading and cooling, providing erosion control, and providing protection from wind. On its Benefits of Trees webpage2, the Arbor Day Foundation lists several reasons why homeowners should consider planting trees. The Nature Conservancy’s Green Heart Project webpage summarizes additional reasons for planting trees in urban settings, including health-promoting functions such as reducing stress.3
From an environmental perspective, trees remove carbon dioxide, one of the greenhouse gases driving our warming climate, by capturing carbon in their roots, trunks, branches, and leaves during photosynthesis and in their wood if they are harvested. A study published in Science in July 2019 makes a case for tree planting as a major tool for addressing global climate change. Using tree cover data and predictive modeling, the study authors estimate the carbon storage impact of reforesting massive swaths of non-urban and non-agricultural land around the world.4
The Science study describes a large-scale solution to a planetary problem. But wha
t is the role of the individual gardener in solving this problem?
Think of planting trees as another way to offset carbon, similar to purchasing airline offsets but longer term. Or comparable to signing up with a renewable energy company as your energy supplier or subscribing to a composting service for your food scraps. A two-inch diameter River Birch (Betula nigra) in excellent condition and planted in full sun in Maryland sequesters 25.17 pounds of carbon dioxide in one year, while a Willow Oak (Quercus phellos) of similar size sequesters 21.82 pounds of CO2.5 Multiply that amount by the lifespan of the tree and it can be significant.
This information is from iTree, a site developed by the U.S. Forest Service and several partner organizations that provides tools for exploring data on tree cover, the capacity of individual tree species to remove air pollutants or reduce runoff, and the volatile organic compounds and other chemicals trees add to the atmosphere. It’s a great site to consult in addition to aesthetic and cultural guides to tree selection, such as The Tree Book by Dirr and Warren.6
To promote residential and community tree planting, several states and counties offer incentives. In the Washington, D.C. metropolitan area, three to check out are Casey Trees, Marylanders Plant Trees, and Arlington County’s Tree Planting Programs.
If your garden is too small for planting trees, or for planting as many as you would like (a scenario easy to imagine), consider sponsoring a commemorative tree on public land. TREE-MENDOUS MARYLAND is one program that encourages individuals to purchase trees for their communities (select the “Gift of Trees” link for instructions).
Privacy, shade, flowers in spring, color in fall, food for insects and birds, an increase in property value – the benefits of trees are numerous. Add now the ability to lock up carbon, not a recently discovered feature but in this era critically significant. Choosing trees first makes good gardening and garden design sense.
Notes
1. Steiner, Rob. “Landscape Design Principles for Residential Gardens: Eight rules for creating a satisfying garden that is neither fussy nor constraining.” Garden Design.
“This article, adapted for the web, originally appeared in the Early Spring 2015 issue of Garden Design Magazine under the title “Rules of the Game.”” Accessed January 1, 2020. https://www.gardendesign.com/landscape-design/rules.html
2. “Benefits of Trees.” Arbor Day Foundation. Accessed January 1, 2020. https://www.arborday.org/trees/benefits.cfm
3. “Benefits of Urban Trees.” Green Heart Project. The Nature Conservancy. Accessed January 1, 2020. https://www.nature.org/en-us/about-us/where-we-work/united-states/kentucky/stories-in-kentucky/green-heart-project/
4. Bastin, Jean-Francois et al. “The global tree restoration potential.” Science. 365 (6448): 76-79.
5. “i-Tree MyTree” and “i-Tree Design.” U.S. Forest Service. Accessed January 1, 2020. https://mytree.itreetools.org/#/ and https://design.itreetools.org/
6. Dirr, Michael A. and Keith S. Warren. The Tree Book. 2019. Portland, Oregon: Timber Press.
If you’d like to read more . . .
Chazdon, Robin and Pedro Brancalion. “Restoring forests as a means to many ends.” Science. 365 (6448): 24-25.
Climate Reports. United Nations. Accessed January 2, 2020. https://www.un.org/en/climatechange/reports.shtml
Crowther Lab. Accessed January 1, 2020. https://www.crowtherlab.com/
Note: The original draft of this post was written on January 1, 2020. All photos were taken at Brookside Gardens, Wheaton, Maryland.
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