Comparison of most common extensive green roof planting methods
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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

This page was last edited on 3 August 2022, at 21:04.