Many tress along the street don’t live very long.
The average life of a street tree surrounded by concrete and asphalt is seven to fifteen years.
Many do survive, but decline rapidly.
Many factors underground determine whether a tree will make it.
If the soil is so compacted that the roots can’t get in, it will surely die. If they can get in there is a better chance of getting the water and nutrients needed to survive.
Another question is whether adequate water supplies are getting into the growing area.
Some of the water comes from underground sources and some from rain, and it is hard to measure where the tree is getting it.
Of course, if the roots get into sewers, they can get everything they need.
If a street tree does survive, it is because its roots have been able to explore a big volume of soil.
Just as with any plant, if the pot is too small it won’t grow well. The roots are very superficial, occupying only the top three feet of soil. Tree roots spread out, not down, if given the chance.
People can help street trees with mulch, water during dry periods and protection from things like dogs and garbage dumpers, which can compact the soil, and bicycle chains, which can rub the thin bark that covers the tree’s growth layers.
Other threats that are directly toxic to the roots are bleach water from the scrub bucket or waste from changing a car’s oil.
The soil can be very gently loosened in the tree hole to make sure there is no crust to prevent absorption.
