Have you heard of yarn bombing?
It is the new 'urban art', an 'acceptable' form of graffiti. (But still illegal?)
Said to have originated in the Netherlands in 2004, yarn bombing, guerrilla knitting, yarn storming, or urban knitting, has since spread internationally.
I found this colourfully decorated tree across the street from my office in Surry Hills, Sydney.
Yarn bombing does not only involve trees but any structure that it's possible to wrap in knitted, crocheted, or wrapped yarn.