Green walls are neither self supporting nor self sustaining, hence "sterile" and "high maintenance". We have different viewpoints on the costs/benefits of green walls as opposed to green planting on the ground. It is all comparative and we disagree on the premise and whole life cost benefits of such schemes so no point in arguing.
However, external green walls are generally made up of hydroponically watered trays of plants. Plant species are chosen for their appearance and suitability to survive in that environment rather than attracting insects and other life. Plants grow and die so need maintaining.
I randomly pulled out a guide to green walls from US designers that sets out benefits but also says
- planted panels are not cheap but can last up to 25 years
- plants can die any time but can expect a life of 5-10 years for most species used
- hydroponic systems must be installed, run and maintained
Quote "Are living green walls difficult to maintain? The simple answer is yes."