Caring for a Roof Terrace and Intensive Green Roof

A planted roof terrace is a garden under tougher conditions: the volume of substrate is limited, wind and sun have a stronger effect than at ground level, and excess water must be drained away reliably. If you know these particularities, a few targeted care measures will let you enjoy your roof garden for years to come.

Irrigation – the most important care task

Containers and planting beds on the roof dry out much faster than garden soil, because wind and sunshine increase evaporation and the roots cannot reach down into the ground. In summer, daily watering may be necessary, so automatic drip irrigation is almost always the better solution on roof terraces. Water thoroughly until water comes out of the container's drainage hole, and check the moisture of the substrate with your finger rather than just by eye – the surface often dries out faster than the root zone. Waterlogging is just as harmful as drought: the drainage holes and drainage layers in the containers must work properly.

Keeping drains and emergency overflows clear

On a roof, drainage is a safety matter: blocked drains can lead to standing water and, in extreme cases, to damage to the roof waterproofing. Check roof drains, gravel strips and emergency overflows several times a year – especially after leaf fall and heavy rain – and remove leaves, leftover substrate and matted roots. Inspection chambers above the drains must remain accessible and must not be planted over or blocked.

Wind and exposure

Wind does not only dry plants out, it can also do mechanical damage: containers tip over, grasses, trees and shrubs break, young shoots are torn off. Choose heavy, stable containers, secure tall plants discreetly where needed and place wind-sensitive species in sheltered corners. Secure or put away sun sails, parasols and light furniture when a storm warning is issued. For plant selection, wind-tolerant, drought-tolerant species have proved their worth – lush large-leaved plants quickly suffer on exposed roofs.

Fertilising and substrate care

The limited volume of substrate is depleted faster than garden soil. In spring, feed permanent plantings in containers and raised beds with slow-release fertiliser, and give perennials and trees and shrubs in intensive green roofs additional feed as the planting requires. If the substrate settles over the years, top it up with structurally stable roof garden substrate – ordinary garden soil compacts too much and becomes too heavy.

Winter protection for container plants

Containers freeze through from all sides – the roots there are much more at risk from frost than in the ground. Protect hardy container plants with fleece, hessian or coconut matting around the pot, stand containers on feet so that drainage water can run off, and move them close to the house wall. Water on frost-free days in winter too: evergreens continue to lose moisture and would otherwise dry out (“frost drought”). Bring tender species indoors in good time – overwinter them in a bright, cool place.