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The following is a short summary of the habitat type and how to create/enhance it to a "good" condition. For an informed position, please refer to official up-to-date Government guidance or the UK Government's Condition Assessment Sheet.
Synonyms: Biodiversity Green Roof, Extensive Green Roof
A Green Roof that has been designed to promote and boost biodiversity. It should have a depth of substrate (not including a blanket or turf) that varies between 80 and 150 mm, with at least 30% of the roof at 150 mm deep. It should be planted and seeded with a wide range of dry grassland wildflowers and Sedum species and have at least a 60:40 ratio of other wildflowers to Sedum. It should also have other habitat features like bricks for nesting bees and logs.
Note that this is defined as an ‘extensive’ Green Rood by The German Landscape Research, Development and Construction Society (FLL), and the Green Roof Organisation (GRO) Code of Practice 2021. It should feature many more wildflowers other than Sedum species, with the other species chosen to promote biodiversity. There should be over 25 different types of wildflower species.
Key Species:
Sedum acre
Sedum anglicum
Sedum forsterianum
Sedum rosea
Sedum villosum
Note: It’s important that no more than 40% of the species are Sedum.
Assessment Questions:
Are there at least 25 different wildlfower species?
Does it have a depth of substrate (not including a blanket or turf) that varies between 80 and 150 mm?
Has it been planted with a range of species, such that Sedum only accounts for less than 40% of the species.
Does it include features to promote biodiversity like logs or bee bricks?
If YES, then it is likely 'Urban - Biodiverse green roof'
How to Create / Enhance to a "Good" condition
For creation advice, please refer to the Green Infrastructure Standards. Pricing information can be found here.
How to get a "moderate" rating
In a management plan aiming to achieve ‘moderate’ condition the plan will show the following:
A variety of flower species will be planted, with a focus on attracting insects like bees and butterflies along with other wildlife. Plants will be selected based on how appropriate they are to the size and design of the green roof. The species mix will ensure that there are flowers at all different times of year, providing nectar through the seasons.
The seed mix will be mostly native species. Where non-native plant species are present, they will not be harmful to wildlife. The planting mix will exclude invasive non-native species (INNS).
How to get a "good rating"
In addition to the characteristics for moderate condition, to get a ‘good’ condition the plan will show the following:
Management will seek to ensure a varied vegetation structure, with at least two physically different habitat elements or vegetation types or heights. The variety will mean that no single vegetation type covers more than 80% of the habitat area.
The management regime will ensure that bare ground will not be the most common habitat type.
There shall be a variation in substrate (e.g. soil, sand, or gravel) depth of between 80-150mm, with at least half of the area at 150mm depth.
There shall be Habitat features (e.g sand piles, stones, gravel piles, logs or rubble piles) in order to provide different micro-climates for plants, insects, and other invertebrates.
How to Create / Enhance to a "Good" condition
Guide 1 - Green Infrastructure Planning and Design Guide
Guide 2 - Green Infrastructure Standards
Guide 3 - Creating Green Roofs for Invertebrates
Please note that this is a simple guide to help identify the habitat. For a definitive description, please refer to UKHab documentation. Joe's Blooms takes no responsibility for the content of external links.