Lilac with brown leaves?
I planted a bloomerang dark purple lilac earlier this year. I believe it has received enough water during the summer since it was a wet summer and I watered it every few days during the periods of it being dry. At the end of August the leaves started to turn dry/brown and I’m starting to wonder if I should move it to a new location. It is planted in the front of my house and receives good afternoon/evening light but no direct light before noon so I’m worried about the moisture on the plant from dew. I also have an ornamental quince planted in this general area and its leaves have historically turned brown in August and I have noticed some disease on my zinnia’s in previous years at the end of summer.
The lilac looks like it is struggling to establish its root system. The leaves show a leaf scorch. However, we have had excessive moisture this season so it is possible you may be dealing with poor planting techniques and site conditions. Lilacs grow best in full sun for best flowering in a well drained soil.
Here are some reasons for decline. Make sure the shrub was not planted too deeply. Dig the planting hole deep enough to accommodate the plant with the top of the root ball level with, or just slightly above, ground level. If the roots are confined within the container, they may not be able to grow into the existing soil. Spread the roots out. Do not add a lot of organic matter into the planting hole. This lets water into the hole quickly but if the surrounding soil is clay then the drainage will be poor and the roots can drown. Backfill the planting hole with the native soil (with maybe a handful of organic amendments, but not much.)
Check soil moisture of newly planted trees and shrubs at least once a week. Soil that is moist or damp to the touch is fine. Make sure mulch is no thicker than several inches and away from the base of the trunk.
If the plant gets less that 6 hours of sun, lift and replant in a new full sun location and look at
the above planting process.
We do not have enough information on the quince and zinnias to answer your question. You may be dealing with poor planting techniques, poor site condtions, or possible fungal issues. You can send us photos so we can see what you may be dealing with.