Hanging meadow points way to cheaper Christchurch rebuild

The hanging meadow display at this week's Christchurch Festival of Flowers. Photo / Daniel Thomson

A hanging meadow planted in wool for the Christchurch Festival of Flowers may be adapted to create more affordable "green walls" for the city rebuild.

The grass and blooms that make up the aerial garden are growing in a felted wool product normally laid on steep slopes to prevent soil erosion.

Urban Designer Craig Pocock who came up with the concept says the hanging garden has already attracted interest from the wool industry and he believes it offers advantages over other vertical gardening systems.

"One of the things the Christchurch City Council has looked at (for the rebuild) is green walls and green roofs, but with the current economy it doesn't stack up to have 'green bling' so this is a cheap way to do it. It could hang on the side of a building, it's like hanging wallpaper.

"Green roofs in New Zealand tend to be limited to flat roofs, but they wouldn't have to be if we used this technology, and it gives you an instant result. It's also transportable, you can roll it up and move it across the country the same way you do with Ready Lawn."

A couple of years ago Pocock created a vertical lawn for the Canterbury Museum by sandwiching a thin synthetic blanket with a built in irrigation system (ECO Rain) between about five layers of felted wool (Biomac) made from wool removed during dagging.

Maccaferri New Zealand Ltd, which makes the ECO Rain and Biomac products and provided them free of charge for the lawn project, loaned Pocock a special machine to stitch all the layers together. "We had to sew it together ourselves in the back of a garage."

Once the museum lawn was taken down, it was plucked clean of grass and went into storage until Pocock resurrected it for the flower festival exhibit.

Watering is a cinch. "We can plug it into a garden hose and irrigate the whole wall in 15 minutes then turn it off."

But he says getting flowers to grow successfully in the wool took a lot of trial and error, and once it got going the grass needed a trim.

"Within four weeks the grass had grown so quickly it was higher than the flowers so we had a group of six ladies with scissors hand cut the entire 28 square metres around all 1000 flowers."

Maccaferri's building products manager Nicholas Simmons says at present the wool-based hanging garden is expensive to make because of the labour content but if there is sufficient demand for it, his company could look at making a commercial version which would cut the cost considerably.

Simmons says Maccaferri's current green walls are made of modular plastic boxes that stand vertically.

"They don't do slopes or shapes and you're restricted to the type of plants you can grow in there. The meadow is a narrower and more flexible product so you can pack it up and move it around and change the shape of it.

"Where architects want to create more flowing shapes or curtains on a building or a structure, then this is where the meadow would come in."

Simmons says the wool green wall could also be used to treat grey water. "Perhaps running kitchen sink waste water through the green wall and using it as a purifier or filter so that the water coming out the end is better for the environment and has all the nasties cleaned out."