To renovate an old lilac tree that has become leggy and overgrown, the most effective method is to prune it drastically in late winter when the plant is dormant. This is often referred to as rejuvenation pruning.
Rejuvenation Pruning for Lilacs
Rejuvenation pruning involves cutting the lilac back severely to encourage new growth.
When to Prune
- Timing: Late winter or early spring, before new growth begins. This allows the plant to focus its energy on producing new shoots.
How to Prune
- Severe Cutback: Prune all the stems to within approximately 12 inches (30 cm) of the ground. This seems drastic, but it encourages vigorous new growth from the base.
- Year One (Post-Pruning): The lilac will likely not flower the year after such a severe pruning. Focus on letting the new shoots grow and establish themselves.
- Year Two and Beyond: New shoots will emerge and begin to develop into stems. Prune away any dead, damaged, or crossing branches. You can also thin out some of the new growth to improve air circulation and sunlight penetration. Expect flowers in subsequent years.
- Alternative Approach (Less Drastic): If you prefer a less drastic approach, you can remove about one-third of the oldest, thickest stems each year for three years. This gradually rejuvenates the lilac without sacrificing all the flowers at once. Cut these stems down to the ground.
Why This Works
- Stimulates New Growth: Cutting back the old stems forces the plant to send up new shoots from the base.
- Improves Air Circulation and Sunlight: Removing dead or crossing branches and thinning out the stems improves air circulation, which helps prevent disease. Sunlight can penetrate the center of the shrub, encouraging more flower production.
Important Considerations
- Soil: Lilacs prefer well-drained soil. Amend the soil with compost if needed to improve drainage and fertility.
- Sunlight: Ensure the renovated lilac receives at least 6 hours of sunlight per day.
- Fertilizer: After pruning, apply a balanced fertilizer to promote healthy growth. Follow the instructions on the fertilizer package.
By following these steps, you can successfully renovate an old, overgrown lilac and restore it to its former glory, promoting healthy growth and abundant blooms for years to come.
