It is true that Cherry Laurel, Prunus laurocerasus, is a trooper and will grow almost anywhere, but that is not the same as looking tip top as a hedge in all situations.
A few yellow leaves here and there are natural, especially in the early years after transplanting when it’s still catching up on root growth.
But rashes of them on an established plant indicate your laurel is not happy about something.
Yellow leaves may or may not be associated with Laurel shot hole.
Phill at Yew Cottage in Ireland, of Garden of the Year 2022 fame, puts it well:
There are two common reasons why Cherry Laurel, known for its lush green foliage, can suffer from yellowing leaves.
- Poor drainage and compacted soil
- Iron deficiency due to chalky / alkaline soil
Poor Drainage and Compacted Soil
These two frequently overlap, but not always: compacted soil can be dry, and uncompacted soil can be waterlogged. It’s all bad for roots.
Waterlogging: Poor drainage leads to stagnant water in the soil with no oxygen, creating the ideal conditions for root rot organisms (especially fungus-like Phytopthera) to attack your plants.
This is fatal for most plants if it isn’t corrected, but Cherry Laurel is so tough that it tends to soldier on with lots of yellow leaves and reduced vigour.
Compacted Soil: Heavily compacted soil is airless, lifeless, and has the nasty combo of draining very poorly when wet, but then resisting water coming in when it dries out!
Both states are terrible for roots.
Iron Deficiency Due to Chalky Soil
Alkaline Soil Conditions: It’s all about the Iron Uptake
Cherry laurels prefer slightly acidic to neutral soils.
They usually also grow well in alkaline, chalky soil, if it is reasonably rich in organic matter and well mulched.
But there’s a risk of iron deficiency in poorly fertile alkaline soil.
So, the problem is not alkaline soil itself, the problem is the iron deficiency it tends to cause.
Troubleshooting
How you respond to yellow leaves on your laurels depends on where they are growing. If they have only been growing in place for a few years, consider digging young plants up to improve the soil and/or replace them.
Digging up a mature hedge is less practical: saving it is better.
Good news: whether your soil is alkaline or not, or whether it’s compacted in that area, it is always a good idea to:
- Mulch the area around plants well. This both feeds the soil, and helps release compaction over time
- Prune the plants lightly, but stronger than a normal trim, to see how the leaves regrow while reducing pressure on the roots
- Where drainage is an issue, install suitable drainage trenches
If you know your soil is chalky / alkaline, then go ahead and drench with a chelated iron foliar feed according to the instructions.
And if they still don’t recover, replace them!