Trees are as much a part of our street environments as fire hydrants, light poles, and sidewalks. They help to define right-of-ways, as well as the age and spirit of a community. Trees are the first thing we see as we enter a neighborhood-they form our first and last impression of a place. They also provide significant ecological and economic benefits that far outweigh the cost of planting and caring for them.
Planting trees along a street can be a difficult task. Streets are cluttered and compacted environments for a growing tree. In addition, there are legal, political, technical, and economical issues to be considered when planting on public property.
Tree selections and planting methods essentially determine how long a tree will live. A species that grows very tall and conflicts with utility lines will suffer from heavy pruning to keep the lines unobstructed. Matching the right species and variety of tree to the site will extend its ability to survive.
Perhaps an even bigger concern is underground. Trees like the American Linden are too big and muscular for sidewalk pits or small planting strips. Final decisions on tree selection should be based on the expected mature size of the tree. The more confined the planting area, the more knowledgeable the planter must be.
Our first street-side planting recommendation is for planting in the street lawn (or tree lawn), between the sidewalk and curb. Our plant area is a five-foot-wide grass strip that extends along the length of the street. The first step in this kind of planting is to loosen the soil and rot-tiller or shovel over an area including the width of the tree lawn and eight feet in length, just as you would if you were planting around your home.
Preparing a tree lawn for planting is like yard planting, but slightly more restricted. The prepared planting area will be a rectangle instead of a circle, and it will not be quite as large. Mark out a five-foot by eight-foot rectangle, and loosen the soil to the depth of the root ball. The ideal planting area looks like the bottom of a bowl (unless drainage is a problem) with the center the same depth as the ball and outer edges only a few inches deep.
Unfortunately, many urban trees do not have tree lawn. Instead they have a wide sidewalk and a small pit of soil every 20 or 30 feet. Because of space restrictions, a "sidewalk pit" presents probably the greatest tree planting challenge. Though there is wide agreement that new, radical approaches to planting in the city are needed, the sad reality is many cities over-restrictive sidewalk pits, or "concrete coffins," are the only street spaces available for tree planting.
As the trees in these existing sidewalk pits die, cities don't have the resources to rebuild street infrastructures to provide adequate root space. There are, however, a few things we can do to increase the life spans of trees planted in these places.