At what stage to shape a box hedge to create a par terre
Hello. I would be grateful for some advice please. Being very interested in the historical background to garden design, I am creating a parterre using box plants. They have been in position now approximately three years but vary in height and depth. Some have reached the height of 35 cm (14") required, others are straggling behind. I know patience is required to attempt such a scheme and but I`m wanting to try and achieve some semblance of the geometric framework as soon as possible. At what stage should I attempt to trim and shape the plants into the formal hedges?