In 1968 John Lennon and Yoko Ono planted two acorns for peace at Coventry Cathedral. The acorns were planted in east and westerly positions, symbolizing the meeting of the couple and the union of their two cultures. This was the first of many peace events that the couple would initiate throughout their lives.
In 1969 John and Yoko mailed acorns and an accompanying letter to a wide variety of prominent figures across the world, asking that the acorns be planted for peace.
One of them was Josip Broz Tito in Yugoslavia. The Museum of Yugoslav History prepared exhibition about this (at the same time with the exhibition about women in socialism. Through the music, documents, photos and objects, the authors wanted to awaken memories of that initiative.
In 2009, forty years after the first one, Yoko Ono recreated the initiative and to send acorns to 123 world leaders and heads of state for world peace.
I could not find data, but hope of all them planted the trees. In the vicinity of the Museum of Yugoslavia there is now forty year old oak. The peace in Yugoslavia, however, did not last that long.