See below for our pick of plants for your green roof with a soil depth of 100mm.
Armeria maritima is at home on cliff ledges and rocky outcrops. This plant is a born survivor, and keeps its tufty leaves all winter. There are cultivars with deeper pink flowers, but the species is the prettiest.
The little Japanese poppy, Papaver nudicaule, is easy to grow – sow it direct or in modules. It’s a short-lived perennial and will self-seed. Alternatively, try the pictured orange California poppies (Eschscholzia californica). Flowers May to June.
Tougher than it looks, Primula auricula is a mountain dweller. It has leathery leaves to withstand rough weather and extremes of heat and cold, and deeper roots than many of its relatives. Flowers from March to May.
Although it needs dry winters, rhodohypoxis is a delightful South African bulb that should be happy in the well-drained conditions of a roof. It spreads by underground stolons to form large, vibrant clumps. Flowers June to July.
If your shed has a pitched roof, then it’s likely one side will get more sun than the other. Choose shade-tolerant plants for the shadier side, or install a mirror to reflect sunlight onto the roof, enabling more sun-loving plants to grow.