Green Roof Planting Options and when is best to use them
Posted by david.luukas
Planting is all about the cultivation of plants which are wind, frost and drought resistant, require very little maintenance and are self-propagating. This type of vegetation will consist primarily of sedums, but can include herbaceous plants and grasses if the substrate depth and location are suitable.
Intensive: Hard and Soft Landscaping
Intensive green roof systems are often a mixture of hard and soft elements; this may include a variety of planting types, from semi-mature trees, lawns, shrubs and herbaceous borders to vegetable beds. Substrate depths can vary from 400-1500mm.
With this variety of planting an automated irrigation system is usually essential. Ponds, paving, lighting, seating and planters can all be accommodated to suit requirements.
Semi-Intensive: Wildflower Mat, Plugs or Seed
As the depth of the substrate is typically 150-200mm on a semi-intensive system, the range of plants that can be utilised on the roof includes a variety of wild flowers, sedum, herbs, grasses and alpines in the form of mat, plugs, seeds and bulbs.
A 40mm drainage layer is used to help increase and retain additional moisture for the plants. Semi-intensive green roofs can offer a more natural look to a planted roof. As with extensive green roofs, a semi-intensive green roof is not designed to be trafficked or to have a permanent irrigation system.
Randomly graduated substrate, from 80-200mm, interspersed variably with shelter stones, aggregate piles, shallow pools and logs in conjunction with specialist seed mixes replicates specific habitats. The objective is to attract specific wildlife species, in accordance with the project’s bio-diversity plan.
NatureMat® is a composite vegetated mat consisting of a biodegradable base layer, a specially formulated substrate layer and a 90% mature plant cover comprising 6 core and 13 randomly sown species (predominantly sedums), grown to maturity in Blackdown’s fields in Somerset. Laid onto a Blackdown substrate and drainage layer, NatureMat® is particularly suited to pitched or curved roofs.
A diverse selection of over 25 species of hardy succulent plug plants, supported by a minimum of 70mm of Blackdown’s extensive substrate and 25mm drainage layer, provides attractive plant cover with a range of colours, shapes, heights and flowering times and periods.
A variety of wild flowers, herbs, grasses, alpines and bulbs can equally be incorporated; varying the substrate depth to suit (70-150mm).
A mix of sedum cuttings, seeds, tackifier and fertiliser are applied through hydroplanting, onto the prepared Blackdown substrate and drainage layer. The plant cover will establish and grow (typically over 1 to 2 growing seasons) to deliver the long-term benefits of a green roof. Particularly suited to restricted budgets and large roof areas.