Picking the right urban tree is harder than it looks

Published 5:39 pm Thursday, September 15, 2022

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Urban trees have a tough row to hoe. Imagine, if you will, living in starvation for most of your life but expected to look your best at all times. That is certainly not the life for me.

This is to what expect from our urban trees. We have codes to go by when building on commercial properties which require a certain number of trees. We have historical districts and home owners associations that require certain trees be left alone or for tree replacements. NC State, along with several other Land Grant Colleges, have tons of research on what species do well and which perform poorly in this situation. However, you always see red maples, sometimes exclusively planted in these areas and they perform horribly.

By the way, a quick visit to the NC Extension Gardener Plant Toolbox will quickly tell you that this is not the place for this tree. Red Maples (Acer rubrum) are an understory tree that like the edge of a swamp. For some reason, they are one of the most planted trees along our streets. Even in the historic district of Washington, you can find them on nearly every street.

So, what are some of the issues that cause these trees to fail? One of the biggest issues is impermeable surfaces. Impermeable surfaces are those that do not allow water to move through them. Think of your house, sidewalks, streets, concrete driveways, and out buildings. None of these are designed to allow the transfer of water through the surface. If the roots of our trees are under that surface, how do they get water? If there isn’t any water, how do they get their nutrition? All of the nutrients that a tree takes up from the soil are dissolved in soil water solution, no water = no nutrients.

If you follow my articles or have taken a class with me, you can probably guess my next issue: right plant in the right place. All too often we choose the wrong plant for the space that we have for it to fit in. We will put plants that love shade in a place where they are receiving direct sun. We may use the example of a red maple here as well. Here is a tree that enjoys being an understory tree, growing in mostly shade on the edge of a swamp and we put it into direct sun in between a sidewalk and a curb. We expect to prosper in an area where it is suffocating to say the least. Many of these trees are planted in a strip that is only three feet wide!

In keeping with the right plant right place issue, is the size of our urban trees. The tree that you are looking at for curb appeal needs to fit the space you have. I like to go to crepe myrtles for this example. This is one of the most abundantly planted trees in the south and for good reason, they are low maintenance and very attractive. However, we have a terrible habit of cutting the tops off of them to keep them in check. The alternative is to plant a variety of crepe myrtle that only grows as large as your space. There are over 96 varieties of crepe myrtle available that grow anywhere from 2 feet to 45 feet. I would guess there is a good chance that there is one that fits your needs.

The last issue that I would like to throw out there, again refers to size, is selecting trees that we place under power lines. This is one that is completely preventable. Folks, there is no way we should be growing trees that get over 15 feet under power lines. This is not only an impractical thing to do, it is dangerous to the lineman that need access to the lines. Let alone the crazy shapes that ensue from the pruning that occurs on these trees.

So, what is one of the best trees that can be grown in a small area? A willow oak (Quercus phellos), is one of the very best that you can use. Of course, these will grow quite large so make certain that you have the space available that they may require. My advice is to do your homework on plant culture and pick the right plant for the right place.

If you are having trouble with growing in your home landscape, call the Extension office at (252)946-0111 or email Gene Fox at gene_fox@ncsu.edu. Topics begin to get slim this time of year, if you have a question, send it in and I may use it for my next article. Happy Gardening!