Answer: The most common reason that lilacs don't bloom is a lack of sunlight, they need full sun (at least 6 hours a day) to flower well. Without sun, all you get are leaves! A good hefty addition of organic matter (compost, composted cow manure, leaf mould) would serve her well. You can also try a fertilizer such as 5-10-10. Preferably, the extended release type made especially for shrubs (I like the brand "Once"). There is also an outside chance that this type of lilac isn't the right type for your area. You could contact a local nursery to check if you have a good variety, and/or check with the nursery or mail order source where you bought the shrub. It is also a possibility that you have purchased a variety that takes along time to bloom so patience is in order.
If you are really desperate, try root pruning the shrub. Next late summer, dig one shovel's depth deep around the drip line of the plant. This will sever some roots and maybe shock the plant into setting flower buds.
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