Meanwhile I did a search online for International Yarn Day and found the website Yarnbombing. They define yarnbombing as the art of knit and crochet graffiti.
Wikipedia gives the following history:
The practice is believed to have originated in the U.S. with Texas knitters trying to find a creative way to use their leftover and unfinished knitting projects, but it has since spread worldwide. The start of this movement has been attributed to Magda Sayeg, 37, from Houston, who says she first got the idea in 2005 when she covered the door handle of her boutique with a custom made cozy.
The movement has been said to be "changing the face of craft" as stitchers are more and more frequently being viewed as fibre artists rather than amateurs or vandals. Joann Matvichuk of Alberta, Canada, invented International Yarnbombing Day, which was first observed on June 11, 2011.
Here are pictures of the trees in Acacia Park.
When I searched images of yarnbombing I came across this marvelous pictures.