The Lilac Tree is a decoration.
It was released as part of the Japanese Event. It was re-released on June 24th, 2011, as part of the FarmVille Birthday Classics event. It was available for 1 day as part of the Japanese Garden theme, on the 9th and last day.
It was re-released on June 2 2012 as free gift for wall post sharing. every time when friends click on your post you will get 1 Lilac Tree and they will get 2 Lilac Tree.