The method of cultivating food on the rooftop is referred to as rooftop farming. It is usually carried out with the help of container gardens, air-dynaponics systems or aeroponics, hydroponics or green roof. Additional platforms known as "aero-bridges" can also be formed between high-rise buildings in addition to the roof space.


Types of Roof Garden
The following are the three basic types of roof gardens classified based on roof vegetation and maintenance.

Extensive roof gardens
This type of roof garden requires minimum layer of soil substrate and hence it is easy to maintain. These gardens are suitable for storehouses, garages, roofs or other additional buildings around the house. At the same time, it has less aesthetical value as the types of vegetation that grow on this is very limited. Lichen and moss are the best-suited vegetation for this type of garden. Lichen can easily grow on surfaces like plastic, metal and glass. Moss, on the other hand, is a small plant that requires less nutrition for its survival and high soil humidity for its growth. This roof garden is less expensive in terms of vegetation types and construction and ideal for a humid climate.

Semi-intensive roof gardens
This type of roof garden requires a deeper soil layer that increases the diversity of plant species. More stable construction is required for this type due to vegetation, greater burden to soil and water retainment. Vegetation can be done with lower species of the Sedum genus. As these species are succulent, they do not need frequent watering. However, vegetation requires additional watering during prolonged dry periods. Wild flowers that do not require maintenance can be grown easily in such roof gardens.

Intensive roof gardens
Vegetation similar to that of a backyard garden like flowers, shrubs, trees and several park elements can be planted in this type of gardens. However, this roof garden requires large, stable constructions and hence most of the buildings are not suitable for intensive roof gardens. Besides basic maintenance needs, it also demands special attention during irrigation.


Roof Garden Maintenance
The maintenance of roof garden is perceived to be one of the major hindrances to their installation. However, it is essential to consider the maintenance schedule during the design process itself as all types of roof gardens require maintenance. All commercial buildings with roof garden are required to undergo roof and gutter checks atleast twice a year. The maintenance rather depends on the desired outcome of the client, which may vary from weekly checks during summer in case of an intensive roof garden to quarterly or even twice yearly checks in case of the most extensive roof garden.

Biodiverse roofs and the roofs designed to be low-maintenance will anyhow require maintenance checks once or twice a year to clean drains and gutters and eliminate unwanted debris. Extensive sedum roofs would require a more intensive maintenance system with an application of fertilizer once a year or weeding three times. However, a less intensive regime of sedum roofs will result upon the development of more mixed vegetation. For extensive roof gardens, it is necessary to develop a wildflower meadow. Low fertility substrates will in turn give rise to short vegetation that does not require cutting back yearly.

The following are some of the key factors to be considered during maintenance:
• Efforts should be made to prevent blockage of drains and growth of undesirable plants.
• Application of fertilizer should be kept to a minimum as high level of utilization may result in increased nutrient levels. which may negatively impact water quality.
• Vegetation barriers are important as they prevent the spread of fire.
• It is necessary to have fall-protection systems as maintenance will be carried out within 2m edge of the roof. These systems are required to be maintained once a year.


Benefits of Roof Garden
The key benefits of a rooftop garden are listed below:
• It converts CO2 emissions
• It produces oxygen
• It reduces the heat of buildings and energy costs
• It creates a habitat for wildlife
• It reduces ambient temperature
• It captures and harvests rainwater
• It reduces storm water runoff and discharge
• It creates large catchment areas.