By Planthappy
United Kingdom 
I have a large leafed Holly bush planted three years ago, it is about 4' high. The leaves on it are turning light coloured and the stems are turning black. It does seem fine below ground level. On the other side of our fence our neighbours are growing leylandi 12' in three years and now overshowdowing our side. Can you tell me is it deseased or are the conditions not right. We are on clay soil.
3 May, 2016
Answers
Agree with Bamboo but suspect the leylandii is removing all nourishment and water from the soil!
3 May, 2016
Your neighbours trees are most likely in contravention of local authority rules - the usual limit for a hedge between gardens is 8 feet -worth investigating?
3 May, 2016
Yes, there are very strict rules in place now regarding the height of leylandii hedges, so contact your local Council to find out where you stand, and to lodge a formal complaint if your neighbour refuses to comply.
3 May, 2016
A photograph or two would be very useful...
3 May, 2016