First can we not use the term defoliate? It scares me when gardeners say that. You can prune now. And you probably should prune now before the plant grows much more if what you want is a more dense growth habit. When you prune, and you probably know this but I'ma tell you anyhow, prune just above the node you want to activate. And don't be afraid of pruning hard. Cannabis can take it. Hope that helps.