I have a purple lilac tree in my backyard. This year it has two or three clusters of white flowers. Is this normal? Will my entire plant turn white? I have been trying to look it up and it says something about grafting? I have lived here for 8 years and this is the first time it has done this.
Most likely your Lilac is a grafted bush and the root stock has sent up a shoot that is of white stock.
You can enjoy the color or try to cut out that portion of the shrub.