Comparison of most common extensive green roof planting methods
Comparison of most common extensive green roof planting methods
Link to this table
| Planting method | Description | Survival rate | Installation labor | Maintenance requirements | Expense | Establishment time | other pros, cons, notes |
|---|---|---|---|---|---|---|---|
| Plugs | Plants in small pots | High | Medium | Low | Low-medium | Quick, 1-2 years depending on species, plug size, and initial planting density | Allows for most flexible and controlled planting design; can be added to green roofs started from cuttings or to pre-grown mats to increase species diversity |
| Cuttings | Small pieces of sedums that are spread across or mixed into growing medium | Good | Low | Low | Low - More than plugs, less than seed | Quick, 1-2 years | Less control over final look than with plugs |
| Seed | Seed | Good | Lowest | Higher | Lowest - Less than plugs or cuttings | Longer than plugs or cuttings – typically 2-5 years depending on species | Less control over final look than with plugs; seed cannot be allowed to dry out until germinated; more bare soil can result in higher weed pressure; need more erosion protection during establishment since soil is bare; only a limited number of species can germinate from seed on a green roof |
| Pregrown Mats | Plants delivered to the site pre-grown into an erosion control mat with growing medium | Good | Low | Low | Low-Medium | Almost instant green | Instant erosion protection if fully vegetated; precise plant composition difficult to predict; less control over final look; less species diversity possible than with plugs, can be combined with plugs to increase species diversity |
| Modular Systems | Plastic, metal, or degradable trays filled with growing medium and delivered to site pre-grown | Good initially | Low | High | High | Almost instant green | Allow for greater precision of design, some may require frequent plant replacement due to edge effect; some trays may retain heat and cause soil to dry out faster, negatively affecting plant health |