Pryapsym: If we're talking about the same thing, topping as a form of pruning, then you have to consider the benefits and the hazards of doing it. It's a common practice but it has it's hazards. Cervantes recommends not doing it within a month of inducing flowering because of the stress it causes. He's got a good explanation on pages 51 to 54. Personally, I would think the strain you're growing and how soon they're going to flower would be strong factors. If it's an autoflowering variety would you? HSA