Trees in the city face a host of unique challenges that they would not face in their natural environment. Horticulturalists have been able to create some new tree varieties that have been able to overcome some of those challenges , but for the most part trees need our help to live healthy fruitful long lived lives in the city.
The average life span of a tree in the city of Portland Oregon is approximately 10 years. The 10th year of a tree’s growth cycle is usually just the beginning of its adult and most productive years. This is in contrast to the potential life span of these same trees, which is usually between 70-200 years (and always more than 10 years). It is fairly obvious by these statistics that our trees are failing to meet their true potential.
Why are they failing to do so? Well, several reasons. First, the Portland Metro continues to grow and with growth and development come the reality that trees must go in order to make room for people. Secondly, some people just don’t like their tree/s. It may be that it is the wrong tree for the wrong location or possibly their just tree haters. These tree hater situations are few and far between. As people learn more and more about the benefits of trees they are eventually won over by them. And if a tree is in a poor location it is not necessarily a bad choice to take it out and start over instead of continuing to propagate someone else’s bad idea. The third and most overwhelmingly common reason trees fail to meet their potential is that they have structural defects or diseases that causes them to decline and eventually NEED to be removed. In most cases these conditions are preventable.
Why so many defects and diseases in our city trees? Well that has to do with those unique challenges of city life we spoke of earlier. For instance, let’s say you plant a tree in the boulevard between the street and the sidewalk. That tree has less room to root in due to the compression of the soil underneath it by traffic on the city street. It also has less permeable soil for the root to absorb oxygen. And due to urban runoff from the lack of permeable soil the tree may become overwhelmed with rain water leading to root rot which can lower the tree’s ability to fight off disease. Decomposition on the of leaves and other matter on the forest floor provides nutrients to a tree in its natural setting. In the city these nutrients are often lacking and urban pollutants often further exacerbate the issue. Also in the city a tree is likely standing alone in instead of being supported by surrounding trees as it would be in a forest setting and so it is not protected from storms. The tree is offered some protection from the surrounding buildings, but this does not protect the tree from heavy storms which are the most likely to lead to structural defects.
The straight fact of the matter is if you would like a long lived tree in the city or if you would like your already long lived tree to stay that way YOU NEED TO MAINTAIN IT. The same way your house needs painting and your roof needs new roofing your tree needs pruning and may depending on your situation also need fertilization, disease prevention treatments, and/or disease treatments. The bad news is that to have your mature trees pruned and maintained correctly by PROFESSIONALS (ei ISA Certified Arborists) is EXPENSIVE (but maybe not so much when you consider the benefits). It is important to hire a professional because incorrect pruning can send you in the other direction causing structural defects and shortening the life of your tree. But the good news is that pruning when done to a healthy tree over time can be limited to every 3-7 years depending on the variety and location. This gives you plenty of time to budget for this expense just as you would budget for a new roof or to have your house painted.
I hope I have done a good job of explaining the importance of maintaining trees in the city and I hope you will consider adding tree pruning and tree maintenance to your home maintenance budget. If you have any further questions you can Ask An Arborist under Contact above.