Planting Trees in Urban Areas

planting trees in urban areas

Slideshow Content
Site assessment for urban tree planting
Basic planting design
Special considerations for urban tree planting
Site preparation
Planting and maintenance techniques

Site Assessment for Urban Tree Planting
Collect detailed information about conditions at previously identified planting sites
Use information to: develop planting plan, determine what to plant, where to plant and what special methods are needed to reduce urban impacts on trees

Impacts of Urbanization on Trees
Air pollution
Poor soils
Exposure to wind
Drought
Flooding/standing water
Increased temperature
Competition
Disease
Damage from humans
Damage from animals
Salt from roads
Inadequate soil volume
Improper maintenance
Conflicts with infrastructure

Urban Reforestation Site Assessment (URSA)
Major Sections:
General site information
Climate
Topography
Vegetation
Soils
Hydrology
Potential planting conflicts
Planting and maintenance logistics
Site sketch

Basic Planting Design
Plant species – diversity is important, select species that are appropriate for the site and tolerant of urban conditions
Plant materials – select from balled and burlapped, container grown, bare root
Plant spacing – based on desired density, should account for plant survival rates
Planting plan – should include species list, sketch, planting dimensions, instructions, supply list, site preparation, schedule and cost estimate

Urban Tree Selection Guide
Specific to the mid-Atlantic and Northeastern U.S.
Used to select species that can tolerate the environmental conditions at the site and perform specific functions
Chart 1: Environmental Conditions - hardiness zone, soil moisture, sun exposure, soil composition, and tolerance of drought, inundation, pests/disease, soil compaction , salt, and pH
Chart 2: Tree Characteristics – growth rate, mature height, canopy spread, form/habit, root structure, fruits, flowers

Example Planting Plan Sketch Source: Omaha Public Power District

Special Considerations for Urban Tree Planting
Calculate soil volume
Evaluate potential for stormwater treatment
Recommend setbacks between trees and infrastructure
Other methods to reduce infrastructure conflicts
Protect trees from human and animal impacts

Calculate Soil Volume
Typical tree pit in an urban area is only 4 feet by 4 feet in area – about 50 ft 3 of soil
Tree roots are typically confined to the pit due to compacted soils
Use designs that provide as much soil as possible for trees

Calculate Soil Volume Source: Jim Urban

Evaluate Potential for Stormwater Treatment
Many urban trees either receive too much stormwater runoff or do not receive enough water because surrounding pipes and pavement direct water away
Stormwater management and planting strategies should be used to manage runoff at planting sites that receive too much water and to direct runoff to other planting sites to provide treatment and reduce irrigation needs

Evaluating Potential for Stormwater Treatment
Sites should be evaluated to determine if they are:
Under-capacity : currently does not receive runoff; runoff bypasses the site in pipe/ditch or is infiltrated
At-capacity : receive sheetflow only
Over-capacity : receive excessive runoff

Recommended Setbacks Between Trees and Infrastructure

Trees vs. Pavement
Tree roots crack or lift pavement if inadequate setbacks are used
10 to 15 foot setbacks are recommended

Trees vs. Utilities
Falling limbs can cause power outages, trees can grow into wires
Maintenance/repair of utilities can damage tree
Recommended setbacks from overhead wires:
10 feet for small trees
15-20 feet for medium trees
20 to 40 feet for large trees
Trees planted under overhead wires must be 10 to 15 feet below the height of the wires at maturity
Recommended setback from underground utilities is 10-15 feet

Trees vs. Sewer and Drainage Pipes
Tree roots can clog or break sewer and drainage pipes –although most damage occurs with older sewer systems
Trees that cause damage to sewer pipes are often removed
Recommended setbacks:
15-25 feet between trees and perforated pipes
10 feet between trees and sewer lines

Trees vs. Buildings
Tree roots may crack foundations if planted too close to buildings
Root growth may become one-sided and cause tree to topple from high winds.
Recommended setbacks:
15 feet for small trees
20-25 feet for large trees

Other Recommended Setbacks
10 foot setback between trees and lighting
10 foot setbacks between trees/shrubs and the centerline of trails (for safety)

Other Methods to Reduce Infrastructure Conflicts
Species selection
Alternative sidewalk design
Alternative sidewalk materials
Root guidance systems
Structural soils
Maintenance strategies

Species Selection
“ The right tree in the right place”
Selecting species with specific characteristics can reduce infrastructure conflicts:
Choose shallow-rooted species when planting near sewer or drainage pipes
When planting near overhead wires, choose species with columnar form
Species with a small trunk flare or root buttress characteristics are ideal for planting next to pavement

Alternative Sidewalk Design

Alternative Sidewalk Materials
Reinforced or thicker concrete slabs
Asphalt
Pervious concrete
Decomposed granite and compacted gravel
Permeable pavers
Recycled rubber
Mulch

Root Guidance Systems
Direct root growth away from infrastructure by restricting root growth laterally or radially, or by directing roots to appropriate areas
Examples: root barriers, root paths, steel plates, root channels, continuous soil trench

Structural Soils Graphic by Matt Arnn

Maintenance Strategies
Use directional pruning instead of topping when pruning trees near overhead wires
Use tunneling as an alternative to trenching when installing or repairing underground utilities near trees
Use alternatives to root pruning to minimize damage to trees

Protect Trees from Human and Animal Impacts
Beaver
Deer
Human Impacts
Lawnmowers
Damage from vehicles
Vandalism
Foot traffic

Protect Trees from Deer

Site Preparation Methods
Trash and debris cleanup
Invasive plant control
Soil amendments

Trash and Debris Cleanup
May be done with volunteers
Evaluate the site to determine the type and volume of trash
Implement measures to prevent future dumping

Invasive Plant Control Methods
Hand removal
Mowing
Heavy equipment removal
Solarization
Girdling
Burning
Chemical
Cultural
Biological

Soil Amendments
Compost : improves water and nutrient-holding capacity, increases nutrients, reduces compaction
Gypsum : decreases soil salinity, increases calcium and sulfur without affecting pH, enhances structure of clay soils
Limestone: decreases soil acidity
Peat: increases organic matter, acidity, and water and nutrient-holding capacity without increasing nutrient content
Sulphur: increases soil acidity

Typical Characteristics of Urban Soils
Severe compaction
Elevated pH
Low organic matter
Low nutrients
Poor drainage
Pollutants may be present
Source: Cornell Urban Horticulture Institute Healthy soil Compacted urban soil

Planting and Maintenance Techniques
Tree planting techniques
Encourage natural regeneration
Maintenance techniques

Tree Planting Techniques
Planting hole must be 2 to 3 times wider than the root ball because roots spread out laterally rather than going deep
Do not plant tree too deep
Technique varies with plant materials and when planting on slopes
Use tree shelters and mulch to protect tree if necessary
Stake only on very windy sites or with top-heavy trees

Tree Planting Specification Copyright International Society of Arboriculture. Used with permission.

Mulching Trees

Natural Regeneration
Natural regeneration is the simplest and cheapest way to reforest: simply stop mowing
In urban areas, poor soils and lots of invasive species and deer can make regeneration difficult
Good candidate sites have: desirable tree seed sources nearby, adequate seed dispersal methods, bare mineral soils with good seed/soil contact, few invasive plants, controlled deer populations, and no sod-forming grasses (e.g., fescue)

Encourage Natural Regeneration
To encourage natural regeneration:
Amend soils problems
Control deer
Control invasive species
Disc soils if sod is present
Install perches to encourage seed dispersal by birds
Supplement with plantings if necessary

Tree Inspection and Maintenance
Post planting and long-term inspection
Watering
Pruning
Weed control
Integrated Pest Management

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Planting Trees in Urban Areas

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