We planted a green roof on the container that we use as an office in November 2018. It is designed as a meadow with perennials and bulbs that grow up to a height of 40 cm. The base is made of grass Sesleria nitida with the addition of flowering perennials and bulbs that withstand drought and sun.
The plants grow in a 15 cm substrate VULKAHUM MIX 80 from the company Humko d.o.o., to which we added the bio-renewable glass wool binder from the company Knauf Insulation d.o.o. We would like to examine whether and how the plants will grow in the 15 cm substrate (a 30 cm substrate would be necessary for a successful growth without the use of glass wool). In the first year, we will water the plants as necessary (manually, since the irrigation system is not installed) and later we expect that the plantation will grow without any additional watering. We also expect that some plants will decay (due to the small quantity of substrate and extreme weather conditions on the roof). Therefore, we also added a larger number of self-seeding perennials, which should grow after the decay of the main plants.
A similar combination of perennials was already used in green roofs abroad, except that a greater substrate depth of 30 cm was used. The glass wool system ensures a larger retention of water in the substrate (the water consumption should be lower by 50 % in comparison to the substrates without glass wool). The 15 cm substrate is usually used for the planting of ground cover perennials, such as Sedum sp., Thymus sp. and similar. But we wanted to create a more diverse and dynamic garden that will act as an organised flowering meadow.