Answer: The most common reasons for failure to bloom are immaturity, lack of sufficient sunlight, pruning at the wrong time of year and over fertilization. I think we've addressed most of these issues so it comes down to immaturity. Sometimes lilacs can take 7 years to bloom so you're almost there. Just continue to give your lilacs good care, prune them in late May or early June to promote lots of new growth (and hopefully flower buds) and withhold fertilizer. I'm sure your shrubs will bloom within the next year or two. Enjoy!
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