Criteria for Selecting trees for Urban Planting

Criteria for Selecting trees for Urban Planting

Urban trees can be defined as those species which are most appropriate for landscaping in urban areas, including in home yards, around commercial or industrial buildings, in parks, as a screen for unsightly land uses, along streets and boulevards, next to sidewalks and in medians.  The degree to which a tree is appropriate will vary depending upon the precise landscaping use.  For example, a tree with a spreading growth habit may be appropriate for a home garden, but not suited to growth along a roadway.

In the selection of tree species for urban planting, the following ten general criteria should be considered:

  1. Trees should be small to moderate size, with an upright growth form, taking into account potential adult size, especially if overhead utility lines are present. 
  2. Trees which do not produce annoying allergens when in flower, or fowl smelling fruits.  
  3. Trees which respond well to pruning and shaping. 
  4. Trees which do not produce large amounts of litter from leaves, flowers or fruits.
  5. Trees which do not produce dripping resin or latex. 
  6. Trees which do not bear large fruits which may fall and cause damage or personal injury. 
  7. Trees which are tolerant of urban air pollution, especially if planted along road ways.
  8. Trees which do not bear sharp spines or leaves close to the ground which could injure a passerby. 
  9. Trees should be tolerant of small limited planting areas, surrounded by pavement, which may deprive them of runoff water and nutrients, impact root development and make them prone to uprooting. 
  10. Trees which do not develop large aggressive surface roots that raise sidewalks or foundations; root barriers can be installed but at some extra expense.

The above list is a daunting one to consider in selecting an urban tree, but not all of the criteria are relevant in all situations.  If a tree is to be planted in your back yard there are very few limitations in terms of its growth form and characteristics, while a tree to be grown in a sidewalk cutout where there is heavy pedestrian traffic will have to be chosen with great care.  

An excellent approach to selecting an urban tree is to observe those already in use in the urban landscape where you live.  If you see a tree you particularly like but are unsure of its identity, take a photograph, note the location in case you wish to return to see it again, and identify it using a gardening reference book or flora, or by visiting a local botanic garden where it may be growing and bear an identity tag.

Another source of information is local municipal government, which may have a helpful street tree selection guide.  The City of San Diego, California, for example, has a listing of recommended urban tree species, grouped into small, medium and large sizes, characterized by form, height, spread, type and drought resistance.  Tree types are identified as deciduous, evergreen, flowering or palm.  Drought resistance is an important consideration since many urban trees are deprived of surface water runoff.

With a little investigation following the suggestions above, along with the TreeWorld plant list descriptions, the gardener can select the ideal urban tree species for any landscaping situation.