Planted the tree 5 years ago. Flowered every year but not this one.
What are possible causes and corrections
Thank you for contacting the Toronto Master Gardeners.
Not knowing your location, the growing conditions of your lilac it is difficult for us to make an assessment. Was your lilac properly pruned. Pruning right after the lilac finished blooming is ensures that you have not removed next years flowers. Lilac flower on “old wood”, wood that was produced the previous season. If you pruned your lilac in the fall or later in the summer you could have removed all the flower buds.
Has anything changed in the lilacs environment. Is it currently being shaded by a mature tree? Lilacs require full sun at least 6 hours for strong flowering. Lilacs thrive in fertile, humus-rich, well-drained, neutral to alkaline soil (at a pH near 7.0). If your soil is in poor condition, add compost to enrich. Learn more about
Lastely, I’m attaching a link to a previous question & answer which should give you all the guidance you need, see below: