Why a Mature Lilac Never Blooms: Sun, Fertilizer, or Pruning?

Troubleshooting a 6-Foot Non-Blooming Lilac

3–4 year old 'Montaigne' lilac in full sun (west side) never blooms. Neighbor's lilac blooms prolifically with no care.

Three Key Checks

1. Sunlight: Verify ≥6 hours direct sun daily.
2. Fertilizer History: High nitrogen (lawn fertilizer) suppresses flowers.
3. Pruning Timing: Only prune right after flowering (or when it would have flowered).

Corrective Fertilization

Apply 5-10-5 (higher phosphorus) now. Results may not show until next year—lilacs set buds on prior year's growth.