Two methods of vertical planting are distinguished.
In the first method (known as green facades), plants grow from the growth substrate (soil or soil replacement) placed below or above the wall. This way, climbing plants are used (they grow up from the soil or a planter) or hanging plants (they hang down from above). The climbing process of plants can be supported by attaching steel cables or frames to the wall.
In the second method (known as the green wall or living wall), the substrate from which the plants grow is integrated into the wall. This way, many more varieties of plants can be used.
Depending on the type of substrate, the following variants can be distinguished:
- No substrate
This technique can be applied to plants that do not need soil to grow. These are plants like tillandsia (air plants) that absorb the necessary water and nutrients from the atmosphere and can withstand long periods of heat and drought. These plants grow slowly and require little maintenance. A structure is placed on the wall to provide mechanical root support for the plants. The plants are then attached to this structure. In some cases, the plants are first grown in the structure and then the structure is installed.
- Loose substrate
The substrate is placed in bags attached to the wall. The plants are then planted in these. Water is administered through irrigation systems. The disadvantage of this technique is that these structures are relatively heavy and the bags can be blown away by strong winds. Therefore, this technique is only used on walls lower than 2.5 metres. The substrate has to be replaced once a year. These systems are mainly suitable for private homes.
- Mat substrate
Mat systems consist of thin mats of coconut fibre or felt. Because they are thin, they can only support plants for three to five years before the roots have grown through the mats or the plants become too heavy for the mat. After that, these systems need to be replaced. Another disadvantage of these systems is that they require a lot of watering. This technique is mainly used on walls up to 2.5 metres high.
- Polyurethane
Polyurethane sheets have high water-holding capacity and remain suitable as a substrate for plants for more than 20 years. A waterproof membrane is applied on the wall side, on which two polyurethane slabs are placed with an irrigation system between them. On the outside, plants are deployed in the slabs.
- Structural substrate
In this technique, plants are planted in 'blocks', which combine the properties of loose substrate with the properties of mats. These blocks can be produced in different shapes and sizes. They have a long lifespan (up to 15 years) and can be easily replaced.
Vertical gardens are suitable for indoor and outdoor spaces and can be applied to existing walls of different heights or as free-standing installations.
The benefits of vertical gardens are: efficient use of available space, lowering urban temperatures, adding an extra layer of insulation to buildings, absorbing noise, purifying air and increasing biodiversity. In addition, vertical gardens have an important aesthetic function and increase the sense of connection with nature.
