Some of my Prunus lusitanica (Portugal laurel) shrubs are changing the color of the foliage and stems. Normally the leaves should be dark green and the stems are a dark cranberry red. The soil here at the coast is very sandy. I have put composted manure (the type from bags), fertilized them, and added a bit of lime to the soil around the trunk and close to the root zone. I have not seen much of a response. Do you know what is the optimal pH for Prunus lusitanica? I am concerned about these shrubs because I just planted them last summer.
Prunus lusitanica tolerates a wide variety of pH and moisture levels in soils. See California Department of Forestry SelecTree webpage about this plant.
According to the webpage of a local Seattle garden writer, the leaves do change color slightly, acquiring a bluish tinge in late fall to winter. She also says that Prunus lusitanica does not like wet feet.
What colors are the leaves turning? You might consider testing the soil, to make sure things are not out of balance. Here is a link to the Miller Library website’s links about soil testing.
Is it possible that the bagged manure was still hot, that is, not fully aged? If so, that could cause problems.
You might also bring in photographs or sample leaves to a Master Gardener Clinic for diagnosis. You can locate a Master Gardener Clinic within Washington State at this website.