Monoculture Problems

Landscape architects will often plant many of the same variety of tree to achieve an effect. In this case, we’ve got the Bradford Pear. They all come into four colors at the same time and it’s beautiful. They all blossom at the same time and it’s gorgeous My name is Blair Glen and I am an ISA certified arborist. This particular complex located in California has an abundant number of these Bradford Pears. They really are a beautiful tree. They are a variety of tree that generally doesn’t get too large so they’re manageable and there are so many benefits to these trees. The original developer thought that he had a great idea and decided to plat this tree as his main tree throughout the complex. The truth be known, there is only four trees in the entirety of this complex. And 65% of them are the Bradford Pear. So why is that a problem? Well, on the one hand if you have an insect or a disease that is associated with this particular variety of tree, it moves in and attacks them all. In this particular case, the problem came when we had an unusual storm in October. The rain was significant and the winds that came after the leaves were wetted were very, very hard. Thirty percent of all the trees in this entire complex took a beating. So now, what do you do? They top all the trees and hope for the best? Do you just top the trees that got hammered? Or do you start over from scratch? Well, the answer here is not that easy. There’s going to be some selective decisions made. Some of the trees such as this one are pretty far gone. Other areas of the complex still look pretty good. However, look at how long and leggy these branches have become. Unfortunately there is an anomaly with this particular tree that makes it somewhat suicidal. The way it grows is that all of the crotches or many of the crotches grow so tight that they end up pushing each other apart so there are inherent weaknesses from this defect. And this is the result. Of ten times the pressure on these two branches that were pushing hard against each other will just pop apart. If it’s in a windstorm or rainstorm, then there’s added leverage. But it can happen even without those added elements of nature. Put these trees around the parking lot or close to buildings and you can have some damage. So let’s get back to the original topic. I threw the word monoculture up there. Why is monoculture a bad thing? If you decide that you want an effect and want a similarity within a complex and do make the decision to use the same tree throughout, then you really have to be prepared for everything timing out at the same time. All these trees do have a life span to the, they all do have problems that seem to come at about the same number of years. By the way, these trees are all less than 30 years old. Had there been an even distribution of different varieties throughout this complex? They would have had the problem here and the problem there. But there would not be any mass problems that all happened at the same time. So, monoculture really is something that isn’t esthetic issue that you should have some consideration. I really don’t recommend that. This concept of an avenue of trees or an archway of trees that are all the same goes way back to ancient England and Europe. There are a lot of beautiful areas where this has been done. But when you have a complex where you have management and maintenance issues, sometimes the wise decision is really not necessarily the one that lead towards someone’s esthetic idea. Thanks for taking the time to view with this brief presentation. My name is Blair Glen and I am an ISA certified arborist.