A street tree is located in the
public right of way, by definition, and does not include trees planted in front
yards or on private property. Too often large investments are made in the
planting of street trees without follow up maintenance to the newly planted
trees. Newly planted trees have the highest mortality rate. Trees provide net
benefits worth 2 to 3 times the cost of planting and caring for them over a 30
year period.
Street trees substantially reduce energy use and provide air
cleansing and pollution reduction for cities that is estimated to be worth
millions of dollars each year. Street trees need the attention of a
well-informed public, they need to be monitored on a regular basis and cared for
in times of stress. Most people, however, do not realize that trees living in
the urban environment need to be cared for. Along with that misunderstanding,
there is the issue of whose responsibility it is to care for the trees. In
addition to their neglect, there is vandalism and lack of respect for the
tree.
Civic participation in street tree care depends on the support of
the larger community, including the city government and private interests.
Fortunately, organizations such as the Massachusetts Commmunity Forestry Council
are working hard to educate and involve the Massachusetts residents in improving
the quality of life and the environment through the planting and care of
trees.
There are many reasons why the survival of the street tree is so
difficult. The main reason is the small size and poor design of the typical tree
pit. The design of the pit is crucial to giving the tree a healthy start to life
in a tough environment. These design deficiencies are starting to be addressed
by experts who are working to create a more hospitable sub-grade environment for
the street tree.
The size of the usual tree pit is a key limiting factor
for tree growth. Roots are restricted in their growth, limiting the amount of
water and nutrients available, as well as compacted too tightly in the soil.
Trees, especially large trees, simply need a larger pit for the trees' root
systems to expand into. This is why we often see buckled and broken sidewalks
around the base of our city trees.
Another problem is the poor soil
condition in the tree pit. The soil composition bears little resemblence to the
soil of the forest and should take into account the climatic conditions of the
environment and the specific needs of the tree. Soil compaction not only limits
the access of air and water to the roots, it contributes to the problem of poor
soil drainage. Most street trees die from overly wet soils that may be due to
sidewalk runoff or compact soil that causes puddles in the pit. Soil compaction
often comes from people walking on top of the pit. Improving soil quality
through organic liquid fertilizations, mulching, watering, and cultivating it
will increase the life of the tree.
Soil contamination is also very
damaging to the tree's longevity. Deicing salt, petroleum products used to clean
the sidewalk, and most problematic, dog waste, are all major contaminants
accumulating in the tree pit.
While designed to protect the tree pit
and/or tree trunk, the grates and guards ironically end up girdling or killing
street trees as the caliper of the tree increases with age. Unfortunately,
maintenance of the tree hardware is almost non-existent.
Watering the
street tree 15 - 20 gallons a week in the late spring through summer,
cultivating and mulching the soil around the tree, pruning the tree, removing
guide wires used to stake the tree, curbing your dog, installing tree pit guards
to protect the soil from compaction, and removing the top half inch of soil at
the end of winter to get rid of the contaminants, are all things people can do
to improve the life and quality of the street trees. Get involved, form
community coalitions designed to protect the street trees in your neighborhood.
It's worth the effort. We cannot take our trees for granted.
Adapted from
the Massachusetts Tree Wardens' and Foresters' Association Bark
newsletter, May 1998 issue.