Tree Assessment/Inventory

One of the benefits of urban forests is their use as a component of storm-water management for streets, medians, parking lots, etc.

Site Factors
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.

Space Considerations
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.

Environmental Considerations
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.

Use of Different Tree Species
Preserving Existing Trees
Guidelines (Medians, Parking Lots)
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