Answer: This would be the normal blooming time -- late April to early May. You may find that your plants have alternating heavy and light blooming years, just as some apple trees alternate. The poor bloom this year could also be attributed to improper pruning, (lilacs should only be pruned in spring right after they bloom or else pruning will remove the next year's blooming wood because they bloom on "old" wood), last year's drought, or increased shade due to the growth of nearby trees or shrubs. Poor fertility can also contribute to lack of bloom.
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