Chapter 4 - Planting the Urban Forest

Three common goals of street tree planting:

Planting in all available spaces, planting a diverse range of species, equalizing the number of trees in neighborhoods across the city

Describe the three main factors to consider when selecting species for planting at a site.

Site factors - soil, climate, slope, elevation; utilities, structures, surface cover, pollution

Economic factors - establishment, maintenance, and removal costs

Social factors - aesthetics, functions, negative characteristics, public safety, neighborhood/community values

Describe the qualities desired for a tree species that will be planted in the narrow space between the curb and sidewalk.

Produces minimal litter, develops minimal basal flare, not prone to developing large surface roots, mature trunk width less than two-thirds the width of the planting strip

What are the key characteristics of good-quality planting stock?

True to type; healthy root system; healthy height-to-caliper ratio; well-developed taper; vertical and radial branch distribution; smooth, bright bark and bright foliage (if normal for species); free of injuries, wounds, pests, and disease

What soil conditions should be assessed and modified, if necessary, before planting?

Test soil to determine chemical and physical characteristics and identify remedial action needed; remove and replace soil if conditions cannot be made adequate to support plants; break up compacted soils; break through impervious layers or install drainage systems to carry water away from plant; if site soil contains less than 5% by weight organics, incorporate composted organic amendment to supplement; correct chemical problems to the extent possible

Describe three methods to create larger rooting volumes for trees planted in paved areas.

Structural load-bearing soil beneath pavement; suspended pavement over noncompacted soils; soil-filled structures below ground that support the pavement above

Describe infrastructure designs that could be used to provide more space for street trees.

Require larger planting spaces in municipal design standards; curve sidewalk to create wider planting areas for trees; create pop-outs into street parking areas at planting locations; use monolithic sidewalks rather than planting strips between the curb and sidewalk; increase ROW width; eliminate the sidewalk on one side of the street; design narrower streets that reserve more space for planting

Providing adequate space for crown development is a function of spacing. Depending on crown form and density, general guidelines for spacing are ___ feet from driveways, alleys, fire hydrants, and ___ feet from intersections

10, 30

What are green roofs? What are their benefits?

Green roofs are plantings designed for tops of structures that increase the urban forest canopy. They provide additional growing space to help mitigate the urban heat island, reduce greenhouse gas emissions, and improve air quality. They also delay and reduce peak stormwater runoff and filter airborne pollutants in rain.

Describe six criteria for selecting large trees for transplanting.

Transplant survival rate of species

Tree size

Tree health, structure, and appearance

Site conditions

Site characteristics

Cost of transplanting

The American Standard for Nursery Stock (ANSI Z60.1) defines a system of:

Measurement, nomenclature, and specification guidelines

T/F: In poorly drained or compacted soils, root barriers have limited effectiveness because roots tend to grow under the bottom of the barrier and then up toward the soil surface

True

T/F: A naturalized invasive plant is a native species that has established and reproduces naturally and degrades the ecosystem

False

An indigenous species is:

a plant species that would occur naturally at the site