There are two key times for lavender pruning. Firstly in late summer to early autumn, when you cut off all the dead flower heads and trim the shrubs back to neaten up. When doing this I make sure that some green growth is left. To encourage an attractive plant I shape them into a mound form by simply giving them a light trim when they look a bit unruly. Spring time we add lime if our ph level reads under 6 and remove any leaves or dead wood from around the plant. Check out Sarah Bader from Lavender at Stonegate video for instructions on how to prune.