Lilacs not Blooming?

What to do when your lilac plant appears healthy but had little or no flowers at blooming time? Try these tips.

Credit: iStock / dimabl

Your lilac plant appears healthy but had little or no flowers at blooming time.

Here are some possible explanations for its lack of bloom:

Your plant is too young and may require two or three years to become mature.

Inadequate sunlight. Lilacs need as much direct sun as possible to ensure mature growth to flower.

When removing flowers, you may have cut back too far. Only cut as far as into the second pair of leaves from the tip of the branch.

Inadequate fertilization. Use an all-purpose fertilizer (high in phosphorus and potassium) just after blooming. Avoid excessive use of high-nitrogen fertilizer or other materials that create too much leaf growth.

Root damage due to planting, construction or nearby digging.

Drying out. Try to keep plants evenly mulched and watered.

Biennial blooming. Flowering in alternate seasons may occur with different cultivars.

Plants are too old. They may need a rejuvenating pruning to encourage young flowering wood. Cut back your lilac hard to within two feet of the base and thin out any weak stems. It will take a couple of seasons to recover but you will wind up with more flowers and they will cover your lilac.

Insect or disease damage. Control accordingly.

Cold winter. The cold may have damaged young flowering shoots.

Conway Lum is a horticulturist at Mandeville Garden Centre in Burnaby. Questions can be emailed to him at clumATcanadawideDOTcom.