Exceptions to the rule
For all the reasons we’ve reviewed, on most of our streets and in most of our communities, we’re better off with lines of street trees, especially in temperate, moderately humid climates. But there are exceptions to this rule. For example, extraordinarily arid places where water is scarce or costly call for other solutions to supplying shade and visual interest, such as narrow streets with buildings brought closer together and cantilevered architectural elements that encroach beyond the building envelope. Fewer trees can also be best for far-north climates where letting more sun in during the many shortened days outranks having shade on the rare warm day. Even in a sunny place where trees grow easily, we might still opt for a unique, skinny, tree-less street here and there in a neighborhood plan, to diversify the addresses and experiences on offer. There are also many kinds of commercial streets and passages, and not all require shade trees; some replace the canopy effect with suspended fabrics, galleries, or portals; others establish the visual interest with creative signs and artwork or palms or flowers instead of shade trees. With or without trees, we also take care to keep clear lines of sight to signage and storefronts on mercantile streets. In Street Design, we also wrote about the usefulness of what Raymond Unwin called the “lean-in” tree, planted in the adjacent garden instead of within the right-of-way.
As with every other detail in city design, context is crucial.
Standard equipment for great cities
When they’re right, they’re right, which is most of the time—so street trees are not just a decorative frill, something to be cut when the budget’s tight. They’re mission-critical equipment in making good, resilient cities and towns, and that’s why they’re number ten on my list of Town Planning Stuff Everyone Needs to Know.
For more information, check out my TEDx talk (it’s a love poem to street trees), and read what John Massengale and I wrote about “The Seven Roles of the Urban Street Tree” in Street Design: The Secret to Great Cities and Towns, or read Henry Arnold’s classic, Trees in Urban Design. --Victor
Episode 10 of Town Planning Stuff Everyone Needs to Know is all about street trees. This episode is illustrated with photos, diagrams and video from Yellow Springs, Ohio; Rochester, Buffalo, Brooklyn and Manhattan, New York; Barcelona, Spain; Washington, DC; Guilin, China; Stockholm, Sweden; Chattanooga, Tennessee; Paris, France; Greenville, SC; and Miami, South Miami, Coral Gables, Lake Wales, and Winter Park, Florida. Next episode: Street-Oriented Architecture.
