Ono joined Herbert Herrity, the Lord Mayor of Liverpool, who was there to plant an English oak tree in honor of Lennon's 58th birthday.
Herrity also presented Ono with the Freedom of the City of Liverpool Scroll, which was officially awarded to Lennon posthumously in 1984, but never delivered.
"This ... is so beautiful," she told Beatles fans and invited guests. Fans gather annually in Strawberry Fields a section of Central Park on Lennon's birthday and other special dates in Beatles history.
"I'm kind of curious about what this tree represents," said Rita McConnachie of Chesterton, Indiana. The professed Beatles fanatic said she thought the event in the park might be part of a publicity stunt to promote the upcoming release of a compilation of previously unreleased Lennon recordings.
Lennon and Ono shared a Manhattan apartment across from the park.
"John was a true Liverpudlian, in every sense of the word, and he was proud of it," said Ono, who left the podium saying, "All you need is love."