There is a post (I don't recall where) that gets into strategy for population management, not growth. Basically you build a 'population warehouse' with cargo spaces and have a transport make the rounds of all your larger populated planets picking up and dropping them off at the storage facility for later use on your colony ships and planets. The greater the population, the greater the growth, no matter how small the percentage. It sounds like a good strategy to me. I've used it in some recent games and while my reproduction rate was not a problem, it really helped to maximize my colonies.
Another option is to up you reproduction rate in the racial setup window. Of course if you've taken over a game then the above strategy is a good starting point.
