After hard pruning, where everything is cut down to about 6 to 8 inches (on grafted plants, be sure to make the cut above the graft union), it will take a few years for the bush to re-establish and fill out, but you should see some nice growth coming up over the years. We’re guessing the 4-foot-growth appeared this year after the hard pruning last winter? For the next few years, perhaps refrain from pruning drastically any further, to allow the plant to re-establish itself. Do, however, continue to remove any dead, diseased, or crossing branches.
In general, if a lilac bush needs just a tiny bit of pruning to keep it in shape, and to encourage bushy growth, you can cut the tips of branches that are too tall back to a side shoot or bud. This will encourage that side shoot to grow outward instead of the tip continuing to grow upward. Deadheading spent flowers can also help the plant focus its energy on growing shoots and new flowers. Remove any suckers that pop up near the base of the plant.
Make sure that the plant has good growing conditions; full sun, as you have, is great for it. Also check if it has well-draining soil. Clay soil can slow its growth. Lilacs do best in neutral soil pH.
Hi, Megan,
After hard pruning, where everything is cut down to about 6 to 8 inches (on grafted plants, be sure to make the cut above the graft union), it will take a few years for the bush to re-establish and fill out, but you should see some nice growth coming up over the years. We’re guessing the 4-foot-growth appeared this year after the hard pruning last winter? For the next few years, perhaps refrain from pruning drastically any further, to allow the plant to re-establish itself. Do, however, continue to remove any dead, diseased, or crossing branches.
In general, if a lilac bush needs just a tiny bit of pruning to keep it in shape, and to encourage bushy growth, you can cut the tips of branches that are too tall back to a side shoot or bud. This will encourage that side shoot to grow outward instead of the tip continuing to grow upward. Deadheading spent flowers can also help the plant focus its energy on growing shoots and new flowers. Remove any suckers that pop up near the base of the plant.
Make sure that the plant has good growing conditions; full sun, as you have, is great for it. Also check if it has well-draining soil. Clay soil can slow its growth. Lilacs do best in neutral soil pH.
Hope this helps!