What is the problem exactly? I have an old timey lilac. It just took several years to bloom and grow well. Did'nt think it was ever going to bloom but it did in its own good time.I know its at least 10 yrs. old. is now abt.8ft. high and has alot of blooms. I did'nt do anything special to it. Just stuck it in the ground and fertilized it a couple of times. Have'nt done that in a couple of years.
vickie

Here in zone 7 I've had no luck with lilacs. The bush did bloom and the fragrance was heavenly but the plant suffered from powdery mildew; it just hated our humid hot summers.