Sedum is in an excellent position among the star plants for the realization of green roofs. There are a very large number of species and varieties of sedum! They are varied, interesting for their foliage and flowering and above all maintenance free! In addition to these many qualities, the sedum adapts just as well to the plain as it does to the mountains or to the coast, and the sedum multiplies very easily by sowing!
How do you build a green roof?
There are more and more roofs or terraces on buildings or modern houses with a sedum cover, this is an installation that is best left to the professionals. But it is of course also possible to green small garden constructions such as garden sheds, garages or even dog houses, whose roof is not always beautiful and which you can easily decorate yourself, with a vegetable mantle.
- Step One – The Frame: A wooden frame should be made around the perimeter of the roof. The height depends on the thickness of the substrate, for sedum a layer of approx. 5 cm is sufficient. If the roof is very steep, intermediate crossbars can be added to better hold the soil. The roof is then reinforced. For this we use a tarpaulin that goes up along the frame.
- Second step – Drainage: Even with a sloping green roof, it is necessary to add a simple drainage system to avoid standing water that makes the whole thing heavier and could rot the plants. You are using a molded polystyrene sheet that must be drilled into the lower part of the frame at the level of the drain, so that the water is drained off at the level of the gutters. Then just add the substrate and sow the sedum seeds.
Note that a green roof does not arise on any roof. The structure must be strong enough to support the weight of the entire installation and the slope must not exceed 35°. Conversely, if you don’t have a slope, make one to allow for proper water flow.
How to Sow Sedum Seeds Properly?
When to sow? To sow your sedum seeds, choose spring, between late April and early June. Sowing is not recommended in summer, except for sowing in shade and with water. Once the warm weather has passed (around September), sowing will be possible again. However, watch out for late summer storms that wash away the seeds.
Tillage: This is perhaps the most important step. Indeed, the seeds of sedum are very fine, the preparation of the soil must therefore be carried out properly and above all adapted to this particularity. Avoid a surface that is too irregular with clods that are too large. In addition, sedum appreciates well-draining soils, so don’t hesitate to add sand or pozzolana to improve its structure.
Sowing the seeds: Sow in a well-refined soil, the seeds pre-mixed with sand to get an even distribution. Count 1 gram of seeds for an area of 3 to 5 m2. Do not bury the seeds, but “plum” them so that they make contact with the soil. For example, you can use a roller or a flat shovel.
Watering and germination: If you want to facilitate germination, you can water in very fine rain. Water little and often until emergence. If water and heat go well together, it will rise fairly quickly. Then growth can be slow and depends on fertility and climate. After the seeds have germinated, gradually limit watering so the plants get used to the conditions and rainfall of their environment.
How to maintain the sedum in the long term?
Sedum is an ideal plant, even for beginners in gardening, as it requires no particular maintenance! Once well in place in the ground, it is enough to let it live quietly from spring when growth resumes, until winter when the flowering stems wither on their own. It is possible to cut them off slightly or let them self-destruct, which protects the foot a little from frostbite. Only one thing is necessary: never let water stagnate at his feet, it would certainly rot him.
As a landscape architect and geographer by training, I am passionate about the plant world and its countless curiosities. Founder of the Rexania blog and activist for gardening in harmony with nature, I am also an Alsatian gardener, ardent defender of ancient, free and reproducible varieties.