Cultural factors and factors related to symbolic and representational associations of trees are also important. However, one
possible critical factor in the planting and distribution of trees in
the urban environment that has not been investigated previously,
and is certainly related to the factors above, is the selection of tree
species available from the nursery industry of the region. People
obtain trees from purveyors, and thus this article examines the
evolution of the selection of trees available from tree nurseries and
seed availability. If there is no stock or seeds locally available, the
burden of finding a desired tree is much higher. Thus we suggest
that a window into which trees are found in the urban fabric may
be by examining nursery catalogs over time.