How do I get a French lilac to bloom?
You do not say how long you have had the lilacs. Lilacs do not bloom until a few years after they are planted or even transplanted. They bloom on one year old wood (stems that have grown from older branches). Any pruning must be done within a few weeks of any blossoms. Lilacs also do not like to be overfertilized. They need full sun and good water (they do not like drought conditions in the summer).