According to experts such as James Urban, a 20” caliper tree will require 1,200 cubic feet of soil in order to thrive. Establishing this much space underground can be especially challenging in urban and suburban settings. Even if there is enough space, the conditions in the soil may not be such that would support root growth. All of the space designated for the roots of a tree must consist of the essential conditions for root growth. If these conditions are not present, then root growth will not occur and the space is wasted.

In urban and suburban settings, it is the challenge and charge of the designer to optimize the conditions of soil in a very specific – often confined – space for the roots of trees. Most often this will mean that oxygen will have to be provided to soil in spaces that would not naturally have an air exchange.

So establishment of urban and suburban trees requires deliberate design of the underground space involved in growing trees.