I have a couple of old lilacs that I pruned a lot last winter. This year they came back with a lot of new growth and a lot of very large leaves. However, no flowers. I tested the soil and its nitrogen is at the excessive level. Could this be the problem? If so, how do I get the nitrogen back to normal? I also planted a couple of new lilac starts near these bushes. They had some growth and new leaves during the summer. We also had a strange summer for rain. We would get 3+ inches of rain every 3 weeks or so but nothing in between and once it overtopped the rain gauge. I watered twice in spring before all of the rains. The ground has been damp nearly all summer and fall. Would this have any effect on their growth? The leaves also developed a silvery white coating in the last few months of summer and fall. If water depletes nitrogen, should I retest before I treat with anything?
Too Much Nitrogen in Lilac Bed
Certified GKH Gardening Expert
Yes, the nitrogen is likely the problem. Excessive nitrogen causes lush growth of foliage but few flowers or fruits.
Water will not flush out the nitrogen unless it results from a recent application of fertilizer. Here are other ways to reduce nitrogen:
The silvery white coating on the leaves is probably lilac powdery mildew. It won't hurt the plant, but here are some remedies that can improve appearance: