Typically, after harvesting it is necessary to replace 30cm of soil, and even then continuous management is said to be difficult due to nutrient runoff, however as we are using “roof soil” containing high-quality fibrous peat which suits the rooftop planting, only 15cm (half of the above) is sufficient, and not only that, the only nutrient it needs is water. Thanks to this, the growth of close to ten plant varieties are quick and the monthly harvest events and planting of seedlings is becoming an event of relaxation for staff.