Street trees in Japan can sometimes look as though they have been cut back surprisingly hard. Thick branches may be removed, leaving a shape that looks very different from a naturally growing tree. To someone from abroad, it can seem excessive. But street trees have to grow under very different conditions from trees in parks or forests. They share limited space with roads, sidewalks, power lines, traffic lights, signs, and buildings.
If branches extend too far over a road, they can get in the way of large vehicles. If they grow too low over a sidewalk, they can obstruct pedestrians or block the view of traffic lights and signs. Large trees can also develop dead branches, and strong winds can cause heavy limbs to break. In places where this could create a danger, keeping trees smaller may take priority over preserving their natural shape.
Fallen leaves are another part of the problem. A row of large street trees can produce a huge amount of leaves in autumn. They collect on roads and sidewalks and can pile up in gutters. Cleaning them takes time and labor, and leaves can sometimes interfere with drainage. The amount of everyday maintenance required is therefore one factor in deciding how large street trees should be allowed to grow.
Japan also experiences typhoons and other periods of strong wind. Where branches could break and fall onto people or vehicles, cutting them back in advance can be reasonable. A street tree cannot be judged only by whether its shape looks beautiful. If its branches are clearly creating problems for traffic or safety, many people would accept fairly heavy pruning as necessary.
That does not mean that cutting a tree back as hard as possible is always a good thing. Removing too many branches can weaken a tree and make it look worse. If its branches are not interfering with traffic, power lines, signs, or other nearby structures, and the tree does not appear to pose any particular danger, seeing it cut almost bare can still make people wonder whether so much pruning was really necessary.
Japanese street trees are sometimes kept relatively small because road safety and day-to-day maintenance have to take priority over allowing trees to grow naturally. But that does not mean that cutting off more branches than necessary is automatically justified.
