We have a lilac tree and for the past fourteen years we have had plenty of green and growth, but very little in the way of flowers. Could you please give me some advice on this matter?
You have been remarkably patient with your lilac tree! After 14 years it should be full flowering every year.
Lilacs are very much suited to the Dunedin climate so this is not the problem. If your lilac tree is growing in heavy shade, it will reduce the tree’s ability to produce flowers. In this case, remove surrounding vegetation to help bring in light, as a 14 year old lilac would be too difficult to transplant to another site. Make sure the ground around the base of the tree is always weed free and add a layer of mulch.
It is important not to over fertilise with high nitrogen fertilisers during the growing season as this will only encourage vegetative growth as opposed to flowering.
Unfortunately, even a severe pruning will not encourage flowering your specimen. Ultimately you might be better to remove the poorly performing lilac and replace it with a new one. Head to your nearest reputable garden centre or nursery and ask for suggestions for a free flowering cultivar of the lilac species.