French lilac not blooming


Gets sun most of the day. It is next to a poplar tree and about 2 feet away are flower beds



Thanks for contacting Toronto Master Gardeners.  There are several reasons why your lilac had few blooms this year.  For example:

  • During pruning last year new buds might have been cut off in error. Lilacs need be to be pruned soon the flowers fade. Cut just below the faded bloom.
  • Using a fertilizer with too much nitrogen and not enough phosphorus on the shrub or the lawn produces green leaves, while hindering blooming.
  • This year there was a late freeze in Toronto which could have knocked the flowers or the start of the flowers right off the bush.
  • Older lilacs lose their vigor and number of blooms as they age.
  • Some insects such as scale insects and borers damage the stems.  You would see evidence of the insects on the leaves of the lilac.

For more information about blooming problems with lilacs please see:

The spots on the stem in the picture don’t really correspond with any pest infestation or disease.  However if you are concerned about the lilac here are some resources to help you assess whether the shrub has an infestation or disease: