Four and a half years ago, a crop of the hardy tillandsia plant was planted on top of Melbourne’s 91-storey Eureka Tower. Planted at a height of 300 meters where the wind factor sucks most of the moisture out of the air, and exposed to heat as high as 85 degrees Celsius, they mostly remain in tact.
The selection of this plant for such a testing location did not come by accident. Originating from the sandy deserts and rocky cliffs of South and Central America, they have evolved to survive in the most extreme of environments.
One such change means that the plants do not need soil to grow, instead attaching themselves to any solid form around them. Rather than taking in nutrients from roots, the plants have little scales called trichomes that can catch water and nutrients from the air around it.
This remarkable adaptation means the plant can survive in hot, sunny weather, with minimal rainwater required to power its growth.
The Eureka Tower crop is part of a series of trials following an air plant installation in 2013 as part of the Melbourne City Arts Grant Project. The aim is to test the ability of air plants to survive in urban conditions.
Can air plants be placed in the built environment?
Longtime tillandsia enthusiast Lloyd Godman is confused as to why the air plants have not yet been used to green the built environment on a large scale.
“We’re excited about the potential of it and the positive effect it can have on the built environment,” he said.
As Australian cities come to understand the wellbeing benefits of green spaces, its ability to cool cities, and the contribution they make to mitigating climate change impacts, many are looking to increase the foliage in their urban environments.
Vertical gardens are on the up for buildings, yet Godman is skeptical about the practicality of some installations. He highlights the cost and physical effort required to maintain them.
Air plant gardens, in comparison, tend to initially cost about the same as a normal vertical garden, yet the ongoing running costs are minimal. Godman says, “we have pretty much proved you can leave them there and forget about them.”
The plant poses very little risk of damage to surrounding building infrastructure, due to the lack of irrigation system and an inability to grow through building materials.
Like all plants, tillandsia help clean the air of pollutants. As they can be fixed using stainless steel and aluminum, no plastics are used in the process.
Compared with a weight of as much as 90 kilograms a sq m for vertical gardens, air plant gardens can be as light as five kilograms a sq m. This makes them easier to affix to sculptures or installations. Godman has created structures that can move across windows or skylights to reduce heat in the summer, before being moved to allow light and warmth in the winter.
Some hiccups still remain
Godman admits that not every experiment has gone to plan. Extreme frost has been one of the elements to kill the plant. Whilst not suitable for every situation, he believes they still deserve a lot more mainstream attention, depending on suitability.
One limit to their popularity may be their silvery coloring – “people want green foliage rather than silver, that’s one of the negatives. But that’s what makes them work, that’s how they’ve evolved,” Godman says.
The plants initially grow slowly, but on flowering they double in size every year or two. The growth can then be harvested and either moved elsewhere or sold.