PLANTING AND MAINTAINING TREES
Approximately 80% of the U.S. population lives in cities. As a result, more and more people are disconnected from natural areas such as forests and are unable to reap the daily benefits they provide. This makes urban trees extremely important for providing shade, removing air pollutants, reducing stormwater runoff, and providing recreational and aesthetic benefits. If you don’t think urban trees are important, consider this:
- Properly placed trees can reduce heating and cooling costs by 10-20% on average within 10-15 years after planting.
- Sales prices of homes with trees increased by 3.5% to 4.5% over similar properties without trees.
- Consumer ratings of retail establishments were up to 80% higher for business districts with street trees and other landscaping.
- Recuperation rates were faster for patients whose windows offered views of a wooded landscape.
- Less violence occurred in public housing where there were trees.
- Trees reduce surface asphalt temperatures by up to 36° F and vehicle cabin temperatures by 47° F.
One problem with sustaining healthy trees in our cities is that the urban landscape can be a very harsh environment and often does not even remotely reflect a tree’s natural growing conditions. In fact, American Forests estimates that the average life expectancy of a downtown urban street tree is just 13 years, while their rural counterparts can live up to 100 years or more. Symptoms of tree decline from urban stressors can take years to appear. Common causes of urban tree mortality include:
- Damage to roots or soils from nearby construction activities
- Air pollution
- Physical damage from lawnmowers, vehicles or vandals
- Damage from disease and insects
- Trees planted in too small a space
- Improper planting techniques
- Tree stakes or grates left on too long
- Poor, compacted soils
- Lack of watering
- Removal or damage during maintenance of nearby utilities or sidewalks
- Competition from invasive plant species
So with all these potential pitfalls, what’s a person to do to make sure the trees they plant live long and healthy lives?
1. Practice good site planning. Consider whether the planting site has adequate space (a good rule of thumb is to provide at least two cubic feet of usable soil for every one square foot of expected mature canopy) and whether the site’s use will create any potential conflicts with trees. Different urban locations may require different considerations for tree planting. Fact sheets are provided below for planting trees in each of these different locations:
- In highway rights of way
- Along local streets
- In parking lots
- On residential lawns
- In parks
- On school grounds
- Along streams and shorelines
- In utility corridors
- In vacant lots
2. Improve the site conditions if necessary. Evaluate the planting site to determine if you need to apply soil amendments (e.g., compost, peat, lime or other material that improves soil drainage and fertility) to improve the soils or to remove invasive species to reduce competition. A site evaluation can be done using the Center for Watershed Protection's Urban Reforestation Site Assessment form and instructions.
3. Choose the right tree species. Select tree species that are appropriate for the climate and site conditions, including soils and sun exposure. Links to tree selection databases for various regions are provided in the Resources section below.
4. Use proper planting techniques and be sure to maintain your tree. Planting a tree is not difficult, but it must be done correctly to ensure tree health. It is just as important to properly maintain the tree after planting, including mulching and watering. One common mistake people make when mulching is to pile up several inches of mulch around the trunk in a sort of mulch "volcano." This holds moisture around the trunk and can cause the trunk to rot or promote disease and insects. The photo below shows the proper way to mulch a tree by spreading 2-4" underneath the tree and keeping the mulch 1-2" away from the base of the trunk. Click here for instructions on planting and maintaining a tree provided by the International Society of Arboriculture.
Resources for Urban Tree Planting and Maintenance
- Urban Watershed Forestry Manual Part 3: Urban Tree Planting Guide, by the Center for Watershed Protection and USDA Forest Service, 2006. This manual provides detailed guidance on urban tree planting, including site assessment, planting design, site preparation, and planting and maintenance techniques.
Watch a video on the correct way to plant a tree by Rob Beideman of Planting America.
- Planting Trees in Urban Areas. This slideshow reviews all aspects of urban tree planting, including site assessment, planting design, site preparation and planting and maintenance techniques and contains speaker notes. Click on the link above to view the slideshow using Slideshare or to download the Powerpoint from Slideshare so you can give the presentation yourself.
- Tips from the Field: Top Ten DOs and DON'Ts of Urban Tree Planting. This fact sheet summarizes important tips and lessons learned from urban tree planting efforts throughout the country.
- Tree Space Design: Growing the Tree Out of the Box, by Casey Trees, 2008.
- Up By Roots: Healthy Soils and Trees in the Built Environment, by James Urban, 2008. Available from the International Society of Arboriculture.
- The Landscape Below Ground. 1994 Proceedings of an International Workshop in Tree Root Development in Urban Soils, presented by the Morris Arboretum. Available from the International Society of Arboriculture.
- The Landscape Below Ground II. 1998 Proceedings of the Second International Workshop in Tree Root Development in Urban Soils, presented by the Morris Arboretum. Available from the International Society of Arboriculture.
- Urban Tree Selection Guide. This searchable database, created by the Center for Watershed Protection, contains tree and shrub species appropriate for planting in urban and suburban locations in the northeastern U.S.
- A climate change tree atlas is available to help determine what to plant that will be adaptable to a changing climate.
Links to Online Tree Selection Tools:
- Urban Forest Ecosystems Institute SelecTree. A tree selection guide for California
- Friends of the Urban Forest tree selector for San Francisco
- University of Minnesota Extension Plant Elements of Design. A plant selection program
- University of Florida Institute of Food and Agricultural Sciences Tree Selector
- University of Connecticut Plant Database of trees, shrubs and vines
- USDA PLANTS Database
- Arbor Day Foundation Tree Wizard
- USDA Forest Service Northeast Region, Rutgers University and University of Florida's Northern Trees