Starting from pavement
Many dense neighborhoods have far more asphalt and concrete than plants: wide roads, parking lots, loading areas, empty courtyards and cracked school yards. Urban greening means converting some of that into planted or permeable space. It is usually done in small steps, parcel by parcel and street by street, rather than as one large project.
The benefits are modest on any single site but can accumulate: shade, softer surfaces, rainwater absorption, habitat for insects and birds, and a more pleasant place to be. They depend on soil, water and care.
Depaving
Depaving removes unneeded pavement and replaces it with soil and plants. Candidates include surplus parking, oversized driveways, the corners of vacant lots and redundant street areas. Steps typically include:
- Check ownership and utilities. Know who controls the site and what is buried beneath.
- Test the soil. Land under pavement is often compacted and may contain fill or contaminants, especially near former industrial uses. Raised beds or imported soil may be needed if contamination is a concern.
- Remove pavement and base material, reuse or recycle it where possible.
- Loosen and amend the soil, then plant.
- Plan for water and upkeep. New plantings need watering until established.
Depaving can be done by volunteers on small sites, though larger jobs generally require contractors. Reduced parking may meet objections, so engagement is important.
Street trees and planting strips
Trees give the biggest shade return per square foot of ground. Tree pits cut into sidewalks need enough soil volume to survive, so larger pits, connected trenches or structural soil systems often perform better than tiny openings. Planting strips between sidewalk and street can host trees, shrubs and grasses and can double as places to collect runoff. Choosing species suited to the site, avoiding overuse of a single species and planning for overhead wires and clearance all affect success. Street tree planting also requires a plan for pruning and replacement.
Green roofs and walls
Where ground is not available, roofs and walls can be used. Green roofs add insulation and slow runoff; their weight and waterproofing requirements mean they are easier on new buildings than old ones. Climbing plants on trellises or green walls can shade facades, although systems that need irrigation and soil in vertical panels are more costly and need more maintenance.
Small and temporary moves
- Planters and parklets. Movable containers can test ideas cheaply.
- Pocket parks. A narrow lot can become a small park.
- Alley greening. Alleys offer long, narrow strips for plantings and permeable paving.
- Schoolyards. Replacing asphalt with planted areas, trees and play features can benefit students and neighbors, subject to supervision and budget.
- Interim uses. Planting on vacant lots can serve until long-term development, though it may be removed later.
Temporary projects can show what residents want and build momentum, but they may not last unless someone is responsible for them.
Making it last
Many greening projects fail not at planting but afterwards: plants die in dry spells, litter builds up, or volunteers move on. Practical safeguards:
- Assign maintenance to a named group and secure a budget before planting.
- Choose tough, locally suitable plants.
- Provide water access.
- Involve nearby residents, who are most likely to notice problems.
Cost and fairness
Greening costs vary widely with scale and site conditions. Depaving small areas can be inexpensive, while engineered tree pits and green roofs cost more. Funding sources include city budgets, stormwater fees, grants and community fundraising. Rules differ by place.
Greener places often become more desirable, which can raise rents and push out the residents who most needed the improvements. Pairing greening with housing protections and involving long-time residents in design help reduce this risk, although there are no guarantees.
Realistic expectations
Planting does not by itself cool a whole district or fix flooding. The effect depends on how much area is converted and how healthy the plants stay. Treating greening as one component of renewal, together with transport, housing and public space, is more realistic than expecting it to carry large goals alone.