The effectiveness of a vertical greenery system depends on several factors, such as:
1. Plant and substrate system
2. Light provision
3. Plant selection
The first problem often encountered by architects and designs is Point 1, choosing a green wall system. Points 2 to 5 are often included in the green wall sales package. The one question to answer will be:
“What should I consider when choosing green wall systems?”
There are many types of vertical greenery systems in the market today, and they offer different functionalities and support for different plant types. For the purpose of this discussion, we will illustrate our points using a generic 50 cm X 50 cm panel system and a generic modular pot system. We will limit the discussion to the following:
a. Effect of system on plants
b. Effect of system on substrate
c. Effect of system on maintainability
Effect of system on plants
How does the green wall system carry its plants? Let us consider the Selaginella genus (Figure 3b). These are mat-forming perennials growing up to 5 to 10 cm tall, bearing small, scale-like leaves giving a fern-like appearance. These plants grow well on the ground as well as on big 50 cm X 50 cm green wall panels (Figure 2).
However, plants from the Aglaonema genus (Figure 3a) are more shrub-like and tend to grow upwards. This will present loading issues for panel systems. Modular pot systems will be more suitable as there is provision for the plant to naturally grow upwards without compromising the integrity of the green wall substructure (Figure 2).
UGL is collaborating with Chop Ching Hin Pte Ltd to compile a list of plants and their suitability on different green wall systems.
Effect of system on substrate
How does the green wall system hold its substrate? If a green wall has no capability to hold its own media, or allow plants to hold and grip on the system, it will be very difficult for the plants to establish itself on the wall. Some panel systems require pre-growing in the nursery for a period of time before installation. This means a time lag between ordering the plants and actually conducting the replacement. When plants are just stuffed into the system, the amount of stress subjected to the root ball is immense. This often leads to very low survival rates for replacement plants (Figure 4).
Effect of system on maintainability
In recent years, many people in the landscape industry have been trying to answer the question of green wall maintainability. There is really no clear answer to that. While some claim to have zero need for maintenance for their green wall products, our view is that as long as plants are involved, be it on the ground or the wall, it will definitely require some form of maintenance.
A common form of maintenance is replacement of plants. An effective green wall system will facilitate this process. If we consider the weight of a 50 cm X 50 cm panel (50 Kg) and a modular pot system (1 Kg), the modular pots will definitely be easier to replace. This will different implications with regards to labour, cost and safety.
There are, of course, many other considerations that we are not able to cover in this article. If you are interested to know more about green wall systems, please contact us at firstname.lastname@example.org for more information.
We will touch on other aspects of choosing an effective green wall system in subsequent articles. Stay tuned.
– Zac Toh
Note:The purpose of this article is to explore issues associated with plants and generic green wall systems. It is not the intention of the author and the administrators of this website to promote or to denounce any particular vertical greenery system or landscape services.
National Parks Board, Vertical greenery for the tropics, 2009.