By Robert J. Gibbs, FASLA, AICP

For most of the late nineteenth and early twentieth centuries, American cities prospered as their region’s center of commerce. Central business districts thrived as shopping destinations by having densely populated cores, mass transportation, large employment centers, on-street parking, and numerous governmental and civic institutions. During the 1960s, America’s larger cities began installing street trees and designer furnishings in an effort to revitalize downtowns in the wake of losing significant market share to suburban shopping centers.

Even though they are a relatively recent phenomenon in many city centers, street trees enhance a downtown’s uniqueness and authenticity. A well-planned, tree-lined urban street contributes to shoppers’ perception that downtown stores offer quality goods and services not commonly found in shopping malls.

Studies dating back to the 1970s, including those by Kathleen Wolf, a research social scientist at the University of Washington, have documented the effects of trees and other plant life on the “restorative experience,” a concept advanced through two interpretations: Stress Reduction Theory and Attention Restoration Theory. The former theory contends that environments containing natural elements reduce levels of “physiological arousal” (stress) in the brain; the latter contends that the presence of vegetation in an environment is “uniquely capable” of effortlessly capturing attention, which allows those elements of the brain used for direct concentration to recuperate. This mitigates what is known as “directed attention fatigue” (DAF), or simply the depletion of the ability to focus on a directed task.

These findings have implications for urban retail areas. It has been proven that shopping, as a goal-oriented activity constrained by many external factors, can induce a stressed state in the consumer. Research has also documented a positive correlation between a shopper’s “mood state” and his or her willingness to buy. Further, the mood state of retail employees correlates with job performance. The vast array of merchandising techniques retailers employ when aggregated across the urban or mall setting can result in DAF, a form of “information overload” that affects the consumer. It has likewise been proven that DAF results in decreased consumer confidence because of poor or rushed purchasing decisions, which may translate into dissatisfaction with a specific store or the overall retail area.

However, street trees alone cannot solve the problems and challenges that commercial urban areas face. Frequently, too much emphasis has been placed on planting street trees and installing decorative streetscape enhancements in an effort to improve retail sales in historic downtowns.

Retailers, shopping center developers, and urban designers have differing opinions regarding the layout and use of trees. Some shopping center developers even design by the “24-inch rule”: any tree is acceptable in any location as long as it is less than 24 inches tall (a metaphor for no street trees of any type).

In some cities, planners have installed short shrub-like trees that block motorists’ and pedestrians’ views of storefronts and signage but fail to provide useful canopies. In some newer and renovated urban centers, trees have either been organized around an abstract grid or randomly scattered according to some new design theory. In each case, trees have been sited without regard for the visibility of signage, storefronts, and civic buildings.

To enhance the sustainability of an urban commercial center, street trees should be carefully located to provide protection from extreme heat, reduce the scale of the street, mitigate the height of tall buildings, and improve the overall aesthetics of the shopping area. Asymmetrically sized sidewalks can respond to local climate conditions: wide sidewalks accommodate more shade in hot climates or the warming sun in colder regions.

Trees are often planted in a 25-30-foot on-center grid, frequently evenly spaced between predetermined street lighting fixtures or curbside parking spaces. While this modular approach contributes to a balanced and organized urban aesthetic, trees frequently cause havoc with retailers and civic buildings. Rather than installing trees at regular intervals in a row, which may inadvertently align with and thus block the view of building entrances, each building’s significant architectural features or signage should be analyzed during the initial site analysis process. Where worthy building features are present, or proposed with new development, a Civic-Commercial C-shaped Zone should be included in site plans.

Proposed street trees, light fixtures, site furnishings, and landscaping should be planted outside of the C-Zone, near or on common property lines, clustered where they can hide blank walls, or spaced to avoid blocking the view of retail entrances, storefront windows, signage, important commercial architectural features, and civic buildings.

As an idealistic young landscape architect early in my career, I designed a textbook perfect streetscape for a small Wisconsin town. Large Linden trees were spaced exactly 25 feet apart, to align with the center of each adjacent parallel parking space and for a continues tree canopy at maturity in 25 years. Street furnishings and flower beds were precisely spaced in a “landscape zone” along the outer edge of the walkway. I was convinced that my design would almost immediately revitalize the then declining business district by creating a human-scaled, beautiful destination for eager shoppers and diners. Adjacent building features, storefronts of commercial signage were not even considered in my design. Symmetry and scale were all that mattered for my brilliant placemaking and hopefully award-winning design.

However, during the tree installation, a hardware store owner taught me a lifelong lesson. One of the new trees directly blocked all views of this historic neon sign from both passing vehicles and pedestrians. The owner explained how he would lose vital business to a competing larger chain store located in a nearby shopping center. Although I did my best to enlighten the businessman that my design would create a “sense of place” to attract many more people to the downtown, and that views of his storefront or sign were not important, or that the trees would eventually grow tall enough to expose his sign after 20 years, he wasn’t buying it and let me know his concerns in no uncertain terms. He was angry, and I knew he was right. I had mistakenly misplaced trees relative to the adjacent facades and commercial signage. One tree even blocked the portico of a historic landmark church. I had made a blunder that provided a lifelong lesson for future urban designs. This approach was later reinforced during my tenure as the director of planning for a major shopping center developer.

It’s almost unbelievable, but many landscape architects and designers still routinely align trees and furnishing in an abstract grid without consideration of the surrounding architecture.

Since the humbling lessons learned during my Wisconsin streetscape design, I have frequently lectured about my C-Zone theory at universities. When possible, I include photographs of local misplaced street trees, often resulting in rapid tree relocations or removal by the city. Below, see 2009 “before” and 2011 “after” photographs of a street tree blocking a luxury store along Worth Avenue, Palm Beach, Florida. The ill-located tree was moved within month of my Palm Beach Chamber of Commerce address on urban retail best practices.

Robert Gibbs, FASLA, is president of the Gibbs Planning Group, which has advised and planned commercial areas in some 500 town centers and historic cities in the U.S. and abroad. Gibbs is a charter member of the Congress for New Urbanism, a lecturer at the Harvard University Graduate School of Design, author of Principles of Urban Retail Planning and Development, and co-author of eight books.