Hi, I have an old standard lilac tree that is getting too big to hold up the branches with the flowers & leaves out. the tree is about 18 years old now….beautifully large round lollipop….but is now too heavy and falling apart. So… I like to know how far in on the individual branches can I cut them back? I have been trimming after every flowering in summer and If I cut back all the smaller outside of branches with all the leaves to only the branch- sticks from center of graph will I kill the tree? or will new smaller branches grow to fill in? the tree is about 8 ft round. Zone 5 Thanks
Lilacs are hardy trees and have a lifespan of more than 100 years so it is most likely that your tree can be rejuvenated. Pruning is done to encourage new growth of both branches and blooms. The best time for maintenance pruning is just after flowering but you may want go a little farther and do rejuvenation pruning which is best done in the late winter or very early spring. The advantage of this timing is that you can more easily see and adjust the shape of the tree when there are no leaves. In the Ask a Master Gardener section of our website, there are clear instructions on pruning in the posting Lilac Tree near the End of Life, posted July1,, 2012 and here is a link to a website that addresses both maintenance and rejuvenation pruning.