Answer: Lilac blooms on old wood, so it should only be pruned immediately after blooming. If the plant was pruned severely it may have been shocked and that, combined with the drought last summer, may have contributed to reduced flowering. These plants also tend to have alternate years of heavier and lighter blooms, so this could also have contributed to reduced flowering. To give your lilac some TLC, give it some compost and/or well rotted manure and/or some complete fertilizer early in the spring and again in late spring, keep a layer of several inches of organic mulch around it, in times of drought water it to keep the soil evenly moist but not soggy, and prune only in late spring. Remove any suckers smaller than a pencil to help the plant direct its energy to a reduced number of larger stems. With luck it will bloom beautifully next year. As an aside, lilacs will not bloom if they are sited in too much shade. If this is the case you might consider transplanting it to a full sun location.
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