Pruning A lilac Plant.
When is the best time to prune a very big Californian Lilac?
With regard to your question on your Californian Lilac,they need to be pruned quite hard every 4 to 5 years to keep them under control,and to keep them flowering at their best.Unfortunately most people do not do this so you often see massive plants over 10 feet tall.
The best time to prune is after they have finished flowering until Christmas. Remove all the dead and diseased branches,plus the very thin ones, then cut the remaining stem back by two thirds.In the spring this will encourage a load of dormant buds to spring into life.You will need to remove some of them by rubbing them off with your thumb as they start to grow. Leave about 6 to 7 of them evenly spaced out through the frame work of the plant.The shoots that are left will grow on and produce flowers as normal. For More information.