I have a five year old laurel hedge in my garden. All of it is fine apart from one bush. Leaves have turned yellow but not all over yet, some are still green. Roots are not waterlogged nor have they been in drought conditions. There is no evidence of pests in the leaves. What is causing this?
The yellowing of the leaves is generally a sign of watering issues; either too much or too little.
Even a few days of drought can cause yellowing leaves.
Active growing takes place March through October, so watering should continue through this period.
Dig down into the soil or push your hand down into the soil. The soil should be moist but not soggy. Is the ground compacted? This can hamper the water from draining away from the roots. If the roots sit in soggy soil, they will die from root rot.
If the soil is compacted you may need to dig the plant up and break up the soil. Amending the soil at that time can help future watering issues.