I transplanted my lilac tree two years ago and every spring and summer its healthy looking the leaves are green but it does no longer flowers and it used to have a beautiful purple flowers.
Do you have any suggestions how I can get my tree to flower again .
You seem to be right outside of their temperature range. It is spectacular that it even continues to grow there. If it is still a manageable size, you may want to dig it up and keep it in container. This may be the only way that you ever will get to see another flowering set. They aren't considered hardy in your area, so the fact that you are able to care for this, and keep it alive is wonderful!