As she walked around, she became fascinated with the field markings for various sports played in the parks.
"There are all these different markings overlapping, it's a wonderful visual I wanted to build on."
She was also interested in how people used the public spaces, especially after living in London, where the public commons were heavily used.
"I'm also trying to inspire new uses."
Fjaerestad is not a painter - most of her work is in sculpture, installation and video.
She says she has always been interested in grass as a social material and the different forms and ways in which it can be manicured.
"It's the grass I'm working with and the space, the paint is the medium I am using this time."
The artwork is based on infographics and visual representations of data collected by Letting Space and Fjaerestad on how people use the parks, their memories of the parks, and ideas for future improvements.
Fjaerestad has never done an artwork this large and her original proposal was for a 100sqm painting but she was encouraged to go bigger - it is now going to fill the area of two football fields.
She is using a water-and-chalk-based paint - the same used for sports-field markings.
The public is invited to play on the painting and do some painting themselves, at the opening day on Sunday, April 19, from noon to 3pm.
There will be a community picnic and a programme of family events, including a dog-walking parade, hula hooping, ki o rahi, face painting, tai chi, music, kite-making, and a history booth.
-For details on the event, visit www.lettingspace.org.nz/projected-fields