The concept of rooftop gardening has become popular in many countries over the years. The popularity has increased as a result of the realization of the many advantages of rooftop gardens. In some states, it’s a requirement that new buildings should have rooftop gardens. Environmental pollution and lack of space are some of the push factors to the concept. Rooftop gardens can be classified into:
- Extensive rooftop garden
- Semi-intensive rooftop garden
- Intensive rooftop garden
Extensive Rooftop Gardens
Extensive rooftop gardens are common in residential properties. The planting medium used is not so thick, as the plants are not deep-rooted. The medium ranges from 1.6 to 6 inches deep. The layers of the planting medium usually include:
- Waterproof layer
- Insulation layer
- Drainage layer
- Plant medium layer
Extensive rooftop gardens are self-sustaining as they require very little maintenance. There is no need for frequent weeding. The installation is also simple. Since it does not have too much load, an extensive rooftop garden can be built on existing roofs. The garden can also be created in other types of buildings such as sheds and garages. Mostly, extensive rooftops are designed for aesthetic purposes, not for functional rooftop spaces.
Different varieties of plants can be grown on mats and later be put on the top of the root, instead of planting them directly. The plants are able to bear adverse weather conditions such as strong winds and drought. Since they require lightweight materials, the selection of types of plants to be grown and the planting medium should be selected carefully. Some of these plants include Succulents and sedums
The best thing about succulents and sedums is that they are drought tolerant. This means that they do not require frequent watering. They are also less prone to pests and other diseases. Some sedum species can go for months without being watered.
Semi-intensive Rooftop Gardens
Semi -intensive rooftop gardens adopt the characteristics of both extensive and intensive gardening. They can support a variety of plants. The type of irrigation systems and the frequency of irrigation depend on the plant species. Apart from sedum, mosses and grass, smaller shrubs and herbs are some of the plants that can be incorporated. The plants require maintenance like pruning and frequent watering.
Intensive Rooftop Gardens
These are popular on large commercial gardens. The thickness of the planting medium range from 8-12 inches. The gardens are suitable for public access areas. They require high levels of installation and maintenance. Some of the maintenance requirements include lawn mowing, weeding and pruning the plants.
In most cases, intensive rooftop gardens have walkways and paths for ease of access. They are common in skyscrapers and other large commercial buildings. Since they are deep, they can support a variety of plants such as trees, shrubs and vegetables. Additional features such as furniture and playgrounds are also supported in intensive rooftop gardens. Intensive rooftop gardens are common in new buildings, as their overall weight tend to be so high; hence, it has to be included in the initial plan of the building. An intensive rooftop garden requires frequent watering or else; the plants will die from the harsh environmental conditions. Some of the plants that can be planted include perennials, shrubs, small trees, and tropical plants. The trees require frequent pruning to avoid overgrowing. Overgrown trees may fall off and cause accidents or provide shade to other plants beneath and have adverse effects on their growth.
Container rooftop gardening is another method of intensive rooftop gardening. The containers selected should be lightweight, with drainage holes for removing excess water. Too much water affects the growth of plants and may also kill them. The planting medium in the containers should be renewed from time to time so that the plants may get enough nutrients every time. One should add Compost and fertilizer frequently. The types of plants suitable for container gardening are limited since they cannot sustain plants with deep roots. Rainwater cannot penetrate through the planting medium in the container well; hence, the plants require frequent watering.
To choose which type of a rooftop garden suitable for your roof, one has to consider the following factors
Structural capabilities of your building
The building has to bear the weight of the planting medium, plants, and weight from people in the garden. A construction professional will help in determining the strength of the building and advise accordingly. Irrigation should be done carefully since it makes the medium heavier. Intensive gardens are common on new premises where their weight has been included in the initial plan. Weight of other features such as furniture, irrigation systems and containers should also be put into consideration:
An intensive rooftop garden will require more money to install and maintain, compared to an extensive garden which requires little maintenance. For the intensive garden, regular watering, pruning, mowing and weeding are required, making it more expensive. Intensive gardens also need a sound irrigation system which may be costly. In extensive gardens, watering is not mandatory, since the plants are usually drought resistant. Therefore, there is no need for an irrigation system.
Weather patterns of your area
The weather conditions of your locality will dictate whether you will have an intensive or extensive garden. In areas with strong winds and drought, an extensive garden will be a great choice, since they do not require regular watering. Windy regions may not be suitable for planting trees as they can break. Similarly, some plants cannot tolerate winter frost.
Purpose of the garden
If you want your garden to be a source of food, it will have to be intensive since you will require a deep medium for the plants and frequent watering. If the garden is for aesthetic purposes, it can be extensive or semi-intensive. If the garden is for the use of relaxation, an intensive rooftop garden will be a perfect choice. With trees, well-manicured lawns provide an excellent place to relax.
Design of your roof
Intensive gardens are ideal for flat rooftops. It would be hard to irrigate plants on a slope since the water will filter down the roof. As a result, plants at the top will be deprived of moisture, while those at the bottom will get excess water. Extensive gardens can be planted on slanted rooftops. Trees and shrubs may not be an appropriate choice for a slanted roof, since they may fall off. Intensive rooftop gardens serve as functional gardens. They can be used to:
- Grow a variety of food such as vegetables , herbs and flowers.
- Provide a good area for relaxation
Whether the rooftop garden is intensive, semi-intensive or extensive, it has many benefits, including:
- Act as insulators. Rooftop gardens protect a building from too much heat or cold. They also act as sound insulators.
- Reduce the risk of leakage of runoff of the roof by absorbing the runoff water.
- A rooftop garden Adds to the value of a building.
- Spending time in a beautiful rooftop garden contributes to an individual’s overall being.
- Can be a source of fresh food in the urban areas where space is limited.
- The plants absorb various environmental pollutants.