A master plan behind covering the Path to Prosperity in shade: Incorporating street trees into the urban design of neighborhoods

In his seminal book "Great Streets", Allan Jacobs wrote "given a limited budget, the most effective expenditure of funds to improve a street would probably be on trees." I couldn't agree more.

This is not simply an exercise in greenwashing or tree-hugging. In fact, when planning for cities one of the more damaging paths to go down is to think that green is always good. It'll be interesting in fact when the current phase of green fancy dies down so we can start to have more rational discussions of what "green" is appropriate in a walkable environment and how much.

But I digress.

Street trees, on the other hand, are a simple intervention that is almost universally of value to walkability. And by street trees I do not mean ornamental, fruit, or flowering trees. Instead, I'm referring to the kind of tree that actually grows tall and provides shade over the sidewalk and the street. The virtues of these trees (or as engineers like to refer to them - fixed hazardous objects) are so numerous that it's a wonder we often don't have more rigorous programs for planting and maintenance. Here's just a few:

-they provide shade and comfort for pedestrians -they cool the pavement, extending its usable life (moderating temperature swings reduce cracking/swelling) -they add beauty to the walking experience

And I'm sure we could go on.

Of course, there are important design issues to consider. First, try not to do too much; a consistent spacing of the same species not only provides a better canopy, but is more harmonious in appearance.

Second, be careful about the space needed for a good quality street tree. A minimum space is usually needed for long-term health (and sidewalk protection), but overdoing it in width is also unnecessary. High quality trees can very often work in 4 or 5' grates or lawns. Again, match the species to the design goals and don't fall back on one-size-fits-all solutions.

One other important thing about trees is that people love to volunteer time to plant them. So in terms of an effort that can be undertaken with fairly minimal expense, consider establishing a tree fund that volunteers can implement. It need not be brain surgery to lay the groundwork for a quality tree canopy.

Finally, a note on maintenance. Simply planting trees alone and letting them grow will not achieve the desired result. Trees do need some form of maintenance, including watering, fertilizing, and especially pruning. Limbing them up as they grow so that the trees grow “over” pedestrians (and building signs) is critical. Sometimes volunteer groups can do this, but often this kind of long-term effort requires a dedicated paid person or persons.

westport 3

Below are two examples of tree use in the Kansas City area. The top example is that of the Westport area, home to many different shops and bars. The bottom picture shows a more residential setting in the Brookside area, south of downtown Kansas City.

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