Green facade growth rates, what can you expect?
When designing new green façade systems a common question is “how long will it take to grow?” The answer to this question depends on a number of factors as the growth rate of plants will vary according to site specific conditions and those of each species of plant being grown.
Variabilities include, but are not limited to, the following:
Orientation: how much sun and/or shade the plants will receive.
Irrigation system: will the plants be watered manually, by an automatic irrigation system or by rainfall only.
Soil conditions: are the plants growing in a rich and well drained growing medium, or is it a poor sandy soil or a waterlogged clay soil?
Maintenance: will the plants be well maintained with scheduled fertiliser, pruning and soil conditioning routine or left unmaintained?
Plant stock: are the plants of good quality or are they unhealthy and lacking vigour?
Species selection: have the plants been chosen with the site conditions in mind? When grown under optimal growing conditions the growth rate of plants on a green façade of course is going to be far greater than when grown under substandard conditions.
We have seen the outcomes of this first hand through various projects Tensile has been involved in.
In the case of ‘One Central Park’ the green façade was broken into floors with each climber/vine only expected to grow 3 m in height. This was achieved in some areas within 2 months, others 6 months and some are still yet to achieve their expected growth. The reason for this variability in the growth rates can be linked to the distinct micro-climates on the building’s façade created by the building’s aspect. The Western façade has seen extraordinary amounts of growth especially the southern edge of this, but as you get closer to the North the growth rates have declined. The perceived reasons for this are two-fold, wind and solar exposure combined with reflected heat from the glazed façade.
'Broadway’, which runs continuous through the city via George Street, is a long urban canyon which funnels the wind straight off the harbour. These higher wind levels combined with the longer solar exposure is creating a more severe climate in which the plants are grown.
Another factor which can be attributed to the different growth rates is the time of planting. The western side was planted first in spring when conditions for planting are more ideal. The northern façade was planted in the summer months when the conditions were less optimal and a greater chance of transplant shock occurring, this factor too may have slowed the initial and subsequent growth of plants grown on this side of the building.
Factors such as irrigation and soil are negated in this instance as both have been designed specifically for the site. The irrigation system is automatically controlled; whilst the growing medium was designed specifically for the project and is the same across all planter beds. Likewise, the quality of the plant stock: The planting palette was specifically chosen for the conditions of the site and pre-grown off-site under conditions that would ready them for site, this was done so as the plants didn’t undergo too much transplanting stress when planted out.
A great example of a successfully designed and planted green façade is SihlCity Shopping Centre carpark in Zurich, Switzerland. Our partner, Jakob Rope Systems, was responsible for managing the project including the design, installation and supply of products for the 23 m high and 25.5 m wide structure. In approximately 4 years the eastern façade of the carpark is now hidden under a blanket of lush, verdant green growth provided by a combination of Wisteria sinensis and Aristolochia sp. This phenomenal growth rate can be credited to the design and implementation of the planting system. Jakob worked closely with the landscape architects to design a system which would provide optimal growing conditions for the chosen plants, among these design considerations was suspending the trellis system some 700 mm off the façade providing sufficient space for the plants to twine themselves around. Additional to this is the fact the plants were grown directly in the ground, not into planter beds. When grown directly into soil there is greater tolerance in watering and soil conditions, i.e. less chance of soil drying out or ‘slumping’ occurring. Regular maintenance ensures the plants remain lush and dense, not becoming ‘leggy’, sparse or overgrown.
Therefore, in answering the question “how long will a green façade take to grow?” it is important to remember it is a living, breathing structure that is as individual as we are. Every green façade Tensile has completed has been unique, therefore the answer of “how long does it take?” only applies to each individual façade. No matter how long it takes, with proper design, planning and execution you can help ensure a successful outcome.
The original article can be found here
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