In the same vein as yarn bombing (which beautifies lamp posts and park benches), guerrilla gardening injects colour and life into forgotten nature strips, empty blocks and neglected council gardens.
Video: Guerrilla Gardening in Brisbane 2008 ABC 7:30 Report
Here is a great video by ABC featuring guerrilla gardeners in Brisbane City. Looking for your own guerrilla troop in Australia? click here to find your nearest co-conspirators.
I can think of many dead spaces in my local area - in particular a median strip running along a main highway that currently 'grows' sand and straw. Would love to see it spontaneously sprout some native plants...