Plant composition for green walls – Light and structure

In our previous article, we have talked about how to determine the effectiveness of vertical greenery systems (Link to article here). Some things to look out for include:

Plant and substrate system
Light provision
Plant selection
Irrigation
Maintainability

The following is an example of green wall failure when one or more factors are not considered.

Some facts about Singapore:

It’s a small country
Green wall and green roof installations are heavily promoted and subsidised
Folks here like to have green walls both in the indoor and outdoor environment

We recently came across an example of green wall failure in a shopping mall located in Singapore. The reason for failure is quite clearly due to the lack of consideration for the following:

Light provision
Plant selection

Light provision

Figure 1 shows a green wall with 1 spotlight mounted on the ceiling. Since the spot light is located above the middle of the green wall and the discharge is rather focused, plants at the periphery will not be able to absorb any lighting.

Judging from the uneven distribution, it is our opinion that the spotlights are meant to be used as visual highlights and not growth lights. Nevertheless, plants in the middle of the green wall can be seen to be doing quite well from the added exposure. Perhaps a lighting strategy that caters to both aesthetics as well as plant health is in order.

Plant Selection

From Figure 1, we can see that whoever selected the plants has not considered the fact that plants may have different physical structures and growth rates.

Figure 2 shows 3 zones where the plants are not growing very well. We can observe that:

Zones 1 and 2 are patchy probably because they have very limited access to light.

Zone 3 may be patchy due to the type of plants used, and that any additional lighting from the spot light is blocked by plants above.

On a separate note, I find the excessive use of Aluminium strips….disturbing.

The plants look squashed (Figure 3). Spacing between planter boxes seems too tight and the ratio of metal strips to plants is disproportionate. There seems to be more metal than plants. This system may not be able to hold plants with long and thick stems.