The need for irrigation (beyond normal rainfall) will depend upon the plants selected, the local climate, and specific weather patterns, roof slope, and which LiveRoof system is selected. In the north temperate zone (Standard system), supplemental irrigation may seldom be required. Even so, we suggest a backup irrigation system in the event of prolonged hot, dry, windy, sunny weather. During long bouts of dry weather, plants can shrink up, desiccate, die and expose soil. This can increase maintenance requirements as weeds can become established in bare soil and supplemental planting may be required. Excessively dry soil also causes the evaporative cooling effect of the green roof to stop.
Irrigating, even once per month during protracted dry weather, can keep your green roof looking its best and pay dividends through maintenance reductions and evaporative cooling. How frequently one must irrigate during protracted hot, dry weather will vary plant material, climate, exposure, wind, temperature, humidity and roof slope. Installing an appropriate irrigation system brings the peace of mind that when irrigation is needed, it can be applied quickly and conveniently.
Note: In areas of predictably hot and dry spring, summer and fall weather, one should always incorporate an irrigation system into the design. But, irrigation should not be used excessively – please consult your local LiveRoof grower for specifics.