Did you know a tall tree is not always a good street tree? (Part 1)

We have two kinds of weather in Singapore, hot and wet, or hot and wetter. In our concrete jungle, most street trees serve the important purpose of providing shade and lowering temperatures.
Ah. Shade. The bigger the tree the better right?
Not quite.
Sure, a large tree looks beautiful if properly maintained, but an poorly maintained large tree, grown in the middle of a city is both a hazard and an eyesore.

Poorly maintained street tree
Provides zero shade
It goes without saying that large trees are not as easy to maintain as smaller ones. Sure, parks need their large, majestic trees to look good, but what about the streets? What is the right sort of street tree for Singapore?
Quite simply, we want stable trees that provide shade. Consider the following trees, they both provide shade, which one is more stable?

Short and tall tree comparison
Okay, they aren’t actually trees, just poorly drawn pictures of trees
“A” is less top heavy and more stable. We want a street tree that is just tall enough to serve its purpose, and no taller than required.
Now consider the following shapes for a tree’s crown, which one is more stable? 

high and low lcr comparison
Ah the wonders of Microsoft Paint
Just like in the previous example, “A” is less top heavy and thus more stable. Arborists call this the Live Crown Ratio, or LCR. It is the proportion of a tree’s height taken up by a tree’s crown. “A” has a 60% LCR, while “B” has a 20% LCR.

LCR explanation
This is my best attempt at explaining LCR okay?
Generally, any tree with an LCR of 50 to 60% is good, but there are exceptions to the rule. After all, not all tree species have the same shape.
There is one last thing to consider for our ideal street tree. Singapore’s streets are full of things that are great for people but not so great for trees. Lampposts, traffic lights, road signs, and double-decker buses, just to name a few.
It would be silly to plant trees that block these things and cause road accidents.
With the above factors in mind, the first photo in this post is actually a good example of a street tree for Singapore. Here it is again, with all the reasons why.

Good street tree
A heritage tree along Tanglin Road
Any future pruning work should focus on reducing or maintaining its height.
In our next post, we shall look at some less ideal examples and talk about what can be done better.