August 19th - 25th
Most hedges should be getting their final trim now, before this year's growth hardens up. However, leave flowering hedges such as fuchsia, so that you can enjoy their blooms a while longer. Fastgrowing conifer hedges such as Leyland and Lawson cypress should also be clipped, except in exposed regions where the extra layer of greenery will help protect them from wind damage.
Keep an eye on trees and shrubs that you have planted this year: make sure that they have enough water during dry spells. The occasional good drenching is more effective than a frequent trickle.