When have you been pruning it? Lilacs bloom on the previous year's growth, so if you're pruning late in the season, there may not be enough time for new buds to form on new growth. I assume you're fertilizing, and sun's not an issue -- perhaps it's time to check with the nursery it came from or a lilac specialty nursery to see if it's an older cultivar that just takes more time to mature?

Jim

Thanks for your reply, Jim. Last year, in desperation, I snipped off a few branch ends. Thought that might scare it into blooming this year but it did not make a difference. It is in full sun, in fertile soil. I apply nutrimulch (local manure enriched mulch product sold by the yard) in the spring but did not apply granular fertilizer because I thought it would stimulate growth rather than bloom.

I received the lilac from a friend who said it was Virginalis. It was either a root sucker or layered cutting. Her shrub blooms very well and is very fragrant.

My white lilac absolutely loves chicken manure mixed with epsom salts and some lime.

Thanks for your suggestions. I will definitely try an application of lime. Lilacs do so well on the prairies and I thought it was due to the cold winter temperatures. Perhaps the alkaline soil of the prairies is also a factor.