The tree was planted in St Sepulchre Gate shortly after the atrocities in 2001 when nearly 3,000 people died in a string of co-ordinated terror attacks on the United States.
This weekend will see memorial events around the world on the 20th anniversary of the tragedy which saw four airliners hijacked and flown into various targets, including the World Trade Center in New York and The Pentagon in Washington.
The horrific events changed the course of world history as television viewers around the world watched the tragedy unfold.
The twin towers of the World Trade Center collapsed after being smashed into by the aircraft following the Al Qaeda led attack.
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The tree, which has a plaque commemorating the victims, will be a place where Doncaster people can remember those who died and leave flowers on Saturday, exactly 20 years on.