Taking Care Of "Street" Trees

In urban environments, street trees add value by reducing traffic noise, lowering energy costs, increasing property values, and purifying the air, not to mention the aesthetic beauty they add to the local community. Some cities have programs aimed at planting and caring for these trees. In other cities, homeowners are responsible for their care and maintenance, either solely, or in partnership with their local city governments. If "street" trees fall under your care, here are some tips for keeping them healthy and looking great.

What Are Street Trees?

In cities and towns, trees growing in the easement area along sidewalks and on boulevards (the area between the sidewalk and the street), are called street trees. The city usually retains ownership of these areas (and these trees), in order to maintain access to city utilities.

Street Tree Stressors

Because of their proximity to human activities, street trees are constantly exposed to a number of stressors not normally faced by trees growing in other areas:

• limited growth space
• compacted soils
• intense heat reflected off nearby buildings and roadways
• car exhaust
• roadways chemicals
• concentrated build-up of particulate matter
• lack of moisture

Although street trees are usually selected based on their ability to withstand tough environmental conditions, providing a little extra care and maintenance can greatly increase their chances of living a long and healthy life.

Watering

Proper watering is essential to maintain the health of any tree-especially newly-planted trees. Concrete and asphalt create run-off, which greatly reduces the amount of water available to nearby trees. You can help street trees develop deep root systems by watering them deeply every 10 days or so throughout the growing season. (Deeper roots are also less likely to damage sidewalks.) To check the moisture level of the soil, dig 4-6 inches deep, about 24 inches from the tree trunk. If the soil is dry, the tree needs water.

Mulching

Adding mulch around street trees adds organic nutrients to the soil, conserves water, and suppresses weeds. Use organic materials (wood chips, chopped leaves, grass clippings) to create a bowl-shaped ring of mulch 4-5 inches deep, starting 6 inches out from the trunk and extending to the drip line. Avoid building a mulch "volcano" (a mound of mulch around the trunk), which can trap moisture near the trunk and promote disease.

Street Tree "Do's and Don'ts"

Don't:

• Remove or prune street trees until you've obtained instructions and clearance from your local government authorities. Due to the placement of overhead powerlines, and underground utilities, often the Department of Parks and Recreation or Forestry Division takes care of maintenance pruning and removing dead trees.

• Park vehicles, boats, or heavy equipment under trees. The weight can crush roots and cause soil compaction, which reduces the ability of water and oxygen to reach the roots.

• Make significant changes in the soil grade near the root zone. Planting ornamentals around a tree is fine (providing local authorities allow it). However, raising or lowering the grade of the soil (e.g. building raised beds or excavating) by only a few inches can drastically affect the amount of water and nutrients delivered to the roots.
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• Attach signs or other objects to street trees that may weaken tree limbs or cause damage to the bark.

Do:

• Use shovels or snow blowers to keep driveways and sidewalks free of snow in the winter. When pedestrian safety becomes and issue, consider using eco-friendly alternatives to traditional rock salt, which is considered harmful to trees, plants, and animals.

• Protect tree trunks from strikes by lawnmowers and trimmers, and avoid using rototillers within the drip line.

• Safeguard branches and roots during construction and landscaping projects.

• Contact local city authorities before planting street trees to determine required setbacks and obtain any necessary permits.