Younger wood on oaks and beeches retains brown leaves longer. That's what makes beech such a good hedging tree. It's still dense in winter. Through regular clipping the wood is constantly renewed and is hence always young. Are your oaks different ages as well as different species?

Younger wood on oaks and beeches retains brown leaves longer. That's what makes beech such a good hedging tree. By clipping the wood is constantly renewed and is hence young. Are you're oaks different ages as well as different foevued.