Plugs have well developed root systems that adapt rapidly to a new substrate and watering regime.
Since finished plants have adapted to the organic soil it is harder for them to acclimate to the more sterile soil.
Plugs are much more cost effective! Plugs are sized to the medium and are inexpensive enough to allow for the plant material cost to remain low.
Most finished plant material available has been grown in a highly organic, commercial nursery medium which is unsuitable for green roofs.
Finished nursery containers can have heavier soil and the extra weight of the plant can exceed the medium’s ability to support it.
Significant amounts of transplant container medium can offset the planned nutrient content for the planting area.
Plugs are perfect for planting in spring, early summer and fall
Plants in a finished nursery container can be rooted too deep for the shallow green roof substrate. Having to cut the roots back defeats the reason for starting with a larger plant.
Organic medium will shrink more rapidly then inorganic mixture, which affects plant survivability
Plugs allow for much greater plant diversity
Plugs can be easily transported and packed into shipping boxes.
Plugs are more environmentally friendly. Reduce waste by just having empty plug trays instead of individual nursery pots.