It is not uncommon to see beautifully designed buildings adorned with some type of vegetation to enhance its façade. From parking structures and shopping centers to hospitals and apartment buildings, roof top plantings can help make an otherwise inanimate structure come to life.
The advantages of implementing a green roof can be economic, environmental, and if nothing else, politically correct. Whether plans call for an extensive or intensive green roof system, one thing is for sure; the plant selection must be well thought out and well designed.
With an intensive green roof system, the sky is the limit. That is, after the structural limits of the building are determined. It is not uncommon to find trees, shrubs and grasses as the plant of choice on many buildings and plaza decks throughout the world.
Extensive green roof systems have proven to be a little more difficult. By minimizing the growing medium to allow for a lighter dead load, we must simultaneously minimize the amount of maintenance and care. Typically the plant species of choice is sedum or stone crop. This plant species is the most drought resistant and freeze resistant plant available.
It is found in most zonal climates and when installed and designed properly can provide a lush natural vegetation layer without the need for continued maintenance.
Things to Consider
Plant Characteristics for Extensive Green Roofs
- Lateral roots not tap roots
- Drought and wind tolerant
- More horizontal growth than vertical
- Not wind blown seeds
- Low nutrition requirements
- Low maintenance requirements
- Light weight at maturity
Plant Selection Criteria
- Geographic region
- Soil depth and composition
- Functional design intent
- Light conditions
- Client desired effect
- Accessibility to the roof by occupants
- Maintenance constraints