From Wiki: In addition to conceptual art, Ono has also created participatory art, including her 1996 project entitled  “Wish Tree” in Japan.

“Wish Piece by Yoko Ono (1996)
Make a wish
Write it down on a piece of paper
Fold it and tie it around a branch of a Wish Tree
Ask your friends to do the same
Keep wishing
Until the branches are covered with wishes”
WISHING YOU A HAPPY BIRTHDAY YOKO!