Answer: Lilacs can sometimes take 7 years to flower so it sounds as though yours is just about there. Maturity dictates when a plant will flower, along with lots of sunshine and ample water. I'd hold back on the fertilizer, though. Nitrogen tends to encourage lots of green growth, at the expense of flowers. Also, be careful about pruning. Lilacs develop flower buds in the late summer for its spring floral display. So, if you need to prune, do it now so the plant can spend the rest of the summer growing and setting flower buds.
As for shocking the plant, I don't think hitting it with a rolled up paper will work, but doing a little root pruning might. Just take your garden shovel and step down hard in a circle about 24" from the trunk, all around the shrub. This will sever some of the feeder roots which will encourage both top growth and root growth.
A final note - why not test your soil's pH? Lilacs grow best in neutral to slightly alkaline soils. If your pH test shows acidic soil, you might try sprinkling some lime over the soil around the lilac this fall. The lime will work its way down over the winter months and help raise the soil's pH.
Hope this information is helpful!
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