Tree Lawn – Concave vs Convex

The following illustrations are of the tree lawn area (or the landscaped area between the curb and the sidewalk) in the Spring Creek TND in Colorado Springs.  Problems with this area include migration of mulch and icy sidewalks on the north facing townhomes (due to lack of sunlight).  I am proposing that instead of the current domed approach (or convex) with the plantings, that we create a depressed area (or concave) for the plantings.  This will accomplish a few objectives:
     1.  Storm run-off will be directed and utilized within the tree lawn instead of pooling on the sidewalks.
     2.  Currently un-irrigated tree island will utilize the stormwater.
     3.  The depressed area will aid in protecting and keeping the mulch within the planter.  Organic mulch may still migrate in our climate, but this will assist in maintaining as much as possible.

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5 Comments

  1. What species are they planting the tree lawn? I suppose that’s the only concern is how much water the plants can take. Our Stapleton tree lawns tend to be flat except the mulched areas within 12″ of the tree are domed.

    Though pretty much all of the plantings that I have done can take as much water as they can get. Even the lower water plants don’t seem to complain in dry Colorado.

  2. Great question Sean. Our tree lawns have a mixture of junipers, cotoneaster, spirea and most recently grow-low sumac. All of these plants would do well in moist conditions in Colorado (because it is such a dry climate), but plant selection is a crucial consideration when depressing a landscaped area. There is typically a tree within each tree lawn space in Spring Creek, which should be domed within a greater depressed area a little bit for the rootball. I have seen some very successful applications in very wet climates such as Portland as well.
    Many times, neigborhoods will incorporate bluegrass in the tree lawns in lieu of shrubs. Depressing the tree lawn is useful in these instances as well however I do not recommend turf in any area narrower than 8-ft.

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