Sparse, stunted lilac leaves
Hello! I have a 20+ year old lilac bush that normally is healthy, but this year, far fewer leaves than usual (like 40-50% fewer) came in. What leaves did come in were about half their usual size. The flower bunches were sparse and about half their size too. Now those sparse leaves are turning yellow, then brown. Some branches still have all green leaves but other branches have all brown leaves. We haven't pruned the shrub in a couple of years, nor have we amended the soil. It sits on the western side of my house in North Portland. Is there anything I can do to bring back its lush, green leaves, if not this year then next year?
Multnomah County Oregon
Thank you for the images.
Yes, your lilac looks really tough. I'm uncertain if anything other than replacing it will work. But since planting a new one at this time (mid-summer) won't gain you anything, consider renovating the shrub this year in hopes of stimulating new growth.
Lilacs also benefit from a deep watering - to at least 8 inches deep - once a month during our dry months.
"To keep your lilacs looking their best, they need to be pruned, fertilized and shaped almost every year, soon after they are done blooming in the late spring." ("Pruning Large, Overgrown Lilacs" has more information - https://hortnews.extension.iastate.edu/1993/2-10-1993/lilac.html)
If your lilac is a multi-stem shrub, consider renovating it by removing the oldest stems at ground level. If you want to try to salvage this rather tired looking shrub, remove 20 percent of the oldest, gnarliest looking stems. The hope is to have new stems sprout from the base to replace the old ones. Such a procedure may require several years to complete.