Answer: You can certainly cut the blooms to enjoy as a bouquet. To help the plant devote more of its energy toward growth rather than seed production, you could also remove spent flowers from the shrub to prevent it from trying to set seed. As the plant matures it will naturally bloom more heavily. Pruning on a young plant is somewhat limited to directing the shape of the plant, and removing any suckers smaller than a pencil. This should be done in spring immediately after the plant blooms. Pruning later in the season will remove wood that should bloom next year because lilacs bloom on "old" wood. With regard to the plant blooming only on one side, it is possible that the nonblooming side was pruned at the wrong time or grew too late in the season to set buds; if it receives less sun that could also explain it.
Q&A Library Searching Tips