Lilac not blooming right
Only part of my lilacs bloom the rest of the Bush is barely starting to bud out.wHite and purple please help
Your Lilac has 2 different flower colors and this would indicate they are grafted onto a root stock.
Both varieties that are grown may have differing 'chill hours' needed for blooming. This certainly would play a part in the timing difference in your plant.
Though it looks like part of the plant, (the white) is ahead of the purple, it looks to be leaving out and should also bloom out.
Here is a link to refresh you care requirements for Lilac.