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Of course they are hand made! Mostly groups do it together, each person knits or crochets a part, often from leftovers from bigger projects like sweaters or blankets. These pieces are then sewn together and finally sewn around the tree / lamp post / whatever.

The names "yarn bombing" and "guerilla knitting" come from the often not very legal origins - the participants didn't ask whether they were allowed to do it. They just did it to make a city more colourful, more livable, more fun. But now often these things happen with official approve because they know that, like you did, people will see and like the fabric on the trees. The trees in their boring winter grey and brown are colourful and fun to look at!

Stunning informations. I am really glad that you share it here. I will go again in the winter time. Then sure they will pup up really nicely. Top!