Cool Corridors Action Guide Step Six:
After Planting, Work Continues

Once trees are in the ground, they require frequent care to assure their survival, and regular maintenance to protect their health.

After Planting, Work Continues

Perhaps the most critical period in the life of a tree starts when it’s first planted. Without care, many seedlings won’t survive more than a season.
Buhtanese refugees planting trees

Walk the corridor

You’ll find some places where shade isn’t cast by trees. Streams (blue assets) can also cool surrounding areas. And buildings and shade structures themselves are inportant producers of shade.

It doesn't have to be green

Along with “built” shade, designers have identified ways to use buildings, street orientation and sidewalk location to create cooler routes.
Bus shelters shade streets in Phoenix
Elements like galleries, overhanging façades, and vegetation can significantly reduce heat stress and improve thermal comfort, especially when combined effectively. Street orientation and placing sidewalks close to buildings can also mitigate extreme heat.
Many municipalities specify how and to what extent new construction shades adjacent areas. Some limit shade coverage on green space, often to promote vegetation growth. But many codes now require structures to provide shade (during certain hours and times of year) over streets, sidewalks, parking lots and rights-of-way.
Research and recommendations on cooling urban canyons
Planting trees in dense urban environments isn’t easy. And it isn’t cheap.
Aside from near-inevitable utility conflicts, trees needs adequate rooting space, nutrients and water. Without all three, urban trees may not live past a dozen years.
Suspended Pavement Solutions

Urban foresters in Montpelier, VT are testing another system, the Stockholm method, to help trees survive under pavement. 

Combine with broad civic initiatives

Because many neighborhoods lack significant tree canopy, the cost to “cool” their corridors may be prohibitive. Some cities, like Phoenix, stage creation of cool corridors to minimize annual expense.
According to the UN Environment Program, planners recommend that cool corridors can be most economically — and perhaps only when — implemented as part of a larger civic initiative.
Trigger Point Baseline Assessment Design and Infrastructure
Planned new development or major redevelopment Greenfield, brownfield, new construction, renovation
Identify natural features, consider opportunities for green site designs
Favor mixed use/transit oriented development, require consideration of shade in building design, assure adequate open space adjacent to rights-of-way, preserve green and blue corridors
City planning, development or revision of climate action plan, transit plan, neighborhood development plan
Assure all city planning process consider green factors and heat impacts, align city departments in a manner that supports coordinated plans and practices, catalog plantable space
Incorporate shade and heat impacts into urban form, identify districts with significant vulnerability to heat
Major city infrastructure initiatives, planning, site design, access, utility placement, building form
Determine whether site selection (or retention) criteria adequately reflect importance of green factors, consider how planners address green factors in site design and construction
Establish requirements for green corridors on city-owned sites, favor building form and design that supports heat mitigation strategies
New or updated codes, policies, code revisions, zoning requirements, subdivision standards, stormwater, resilience, utility improvements
Analyze all plans and planning processes to assess to what extent and how heat impacts are considered, review and improve stakeholder engagement in policy development
Adapt existing or adopt new codes and policies to maximize use of nature-based solutions to climate impacts, incorporate language that supports development of cool corridors
Land sales and acquisitions
Map both public and private natural lands, forest patches, existing pedestrian corridors, trails and parks
Favor acquisitions and management options that protect green and blue spaces
Because many neighborhoods lack significant tree canopy, the cost to “cool” their corridors may be prohibitive. Some cities, like Phoenix, stage creation of cool corridors to minimize annual expense.

Private Land

In virtually all cities most of the existing tree canopy and plantable space exists on privately-owned property. Already developed or not, these lands abut both major and minor transportation corridors.

To cool these routes, cities can rely on street trees but many require front yard trees in new construction and permits to remove shade trees from existing private properties.

Atlanta Tree Ordinance 2022

Text of completed ordinance

Highlights

Streets and other external heat islands shall be shaded by new or existing trees at spacing not to exceed 35 feet on center on average, with a minimum of two trees per lot when feasible. Street trees shall be planted as close to the street as practicable. Internal heat islands shall be shaded at a minimum rate of 1 tree per 750 square feet of heat island area.

Perhaps the most critical period in the life of a tree starts when it’s first planted. Without care, many seedlings won’t survive more than a season.

Early survival

Most trees — even if they look large — will need to be watered regularly during the first year or so. Arborists can provide advice on care for new trees depending on the species planted and your local ecology.

Guide to care of newly planted trees

By now you’re probably working with skilled arborists from the city or other nonprofit groups. Local conservation districts can serve as another source of advice — especially in more rural areas. 

Conservation District Directory

As they mature

Like people, trees grow up and sometimes they too suffer health and growth issues. That’s why regular cyclical maintenance is key to trees’ long-term health. And the older a tree gets, the more benefits it provides to the people and wildlife who live near it.
Volunteer using handheld digital assistant to enter tree data during inventory.

Why cyclical?

City forestry departments often lack the resources to visit every public or street tree on a regular basis.
Instead, they mostly provide public tree maintenance to people who request it. Requesters tend to live in wealthier areas, while people who live in lower-income neighborhoods are less likely to call.
The end result: more healthy tree canopy in some neighborhoods; less canopy in others. In human terms, persistent tree inequities, hotter summers, poorer health.

Learn more: Urban Tree Monitoring: A Resource Guide

Cool Corridors not only make neighborhoods more liveable — they also will save lives among residents most burdened by the impact of climate change.

Review the Six Steps to creating Cool Corridors
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Related Resources

  • Guides

Tree Equity Funding Action Guide
Resource Library