Autumn is the best time for cutting back Escallonia, after they have
finished flowering. Escallonia does make an excellent hedge but you
have a choice between formality and flowers. If you chose a formal
hedge, you'll still get flowers but would get more if you only lightly
trim, removing just the flowering growths when they are over.

If you wish to maintain a formal hedge, you should prune fairly hard to
your desired shape in the Autumn after flowering.

Garden Oasis
www.gardenoasis.co.uk