Garden Q&A: My purple-leaved cherry and lilac shrubs don't flower

Whether you're a gardening beginner or expert, Irish Examiner columnist Peter Dowdall has the answer to your questions

Purple-leaved cherry, left; lilac in bloom, right. File pictures

Question

Why is my mature purple-leaved cherry non-flowering? It really never produced anything significant. Also, I have many lilac shrubs, which also never flower. Both are many years old.

Answer

If your purple-leaved cherry and lilac shrubs are not flowering, the most likely causes are lack of sunlight, overfeeding with nitrogen, or incorrect pruning.

Both plants need full sun to develop flower buds. If they’re in shade or partial shade, they may grow well but won’t bloom. 

Overfeeding, especially with nitrogen-rich fertilisers or lawn feed nearby, encourages leafy growth at the expense of flowers. Instead, use a plant food which is rich in potassium in spring. 

Lilac.

The timing of pruning is also important, particularly for lilacs. If they are pruned in late summer or autumn, the flower buds which form soon after flowering may be cut off before they get a chance to bloom. 

Purple-leaved bird cherry. 

Some varieties of purple-leaved cherry are also selected more for their foliage colour than their floral display, so they may naturally flower only lightly or not at all.

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