One of the benefits of urban
forests is their use as a component of storm-water management for
streets, medians, parking lots, etc.
Trees that are planted in medians and parking lots have to
endure harsh conditions. This includes compacted soil low in needed
nutrients. These soils also tend to vary between excessively drained,
due to the site being built into a mound, or poorly drained because
the site is in a concave formation. Trees that grow naturally in
bottomland conditions are best suited for these sites because they
have adapted to low oxygen or compacted soils. Often the most limiting
factor for urban trees is root space. Therefore, consideration should
be taken to provide space for roots to grow and expand. This can
be accomplished in grids or channels and connected to buffers, rain
gardens and other natural areas. Planting sites should have individual
assessments and species recommendations since numerous species are
suitable depending on objectives.
When planting for streets, medians, parking lots and shopping
centers, above ground portions of trees should be restricted in
size and shape to avoid viewing obstructions for both pedestrians
and drivers. Also, the below ground portions must be restricted
so as not to exceed the available planting area. Upright, oval or
vase-like crowns are preferred over spreading, pyramidal, weeping
and rounded forms. Choosing the appropriate tree species and proper
placement will help to keep maintenance costs, such as pruning or
tree removal, at a minimum.
Trees considered for planting in these areas should be resistant
to air pollution from vehicles and industry. Of course, planting
a variety of species will increase diversity and provide obvious
wildlife and aesthetic benefits. Another benefit of diverse plantings
is the decrease in the chance for losses due to insects and diseases.
Trees in urban areas should also be drought and wind resistant.
Tolerant species will promote the success of these plantings.
In order to promote the establishment and growth of trees on
medians, maintenance should be an important consideration. When
tree stands are established, shading will affect the understory,
resulting in less need for mowing. However, when hardwoods are planted,
leaf litter that carries beyond the median becomes a problem. Although
most of the leaf litter can be recycled back into the site to supply
nutrients to the trees, care should be taken so that it does not
cause problems in the maintenance of the area.
You can click here
for a sample listing of trees suited for planting on medians, parking
lots and shopping centers.