@deangelobaker1988 Well if you're trying to shove as many as possible in there then 9 will physically fit, but the plants would need to be very small and you'd spend more time watering and more money on soil with more containers. A more comfortable fit is 4 plants in a 3x3 and even then the plants will need to be on the smaller size. Hope that helps.
What can I use with roots organic 707
Depends on the size grow pot.