It looks like the container you have is fairly small. If it were a lot bigger, like a small garbage can (15-20 gallon) you might be able to grow that many plants in one container. All the roots would be fine. But 8 in a small container will get root bound big time. I had everyone going nuts that I had two in one container. Best is one in each container and if you're going to transplant you better do it real quick and put each one in at least a 3 gallon container. And when you do fill them up to just a little below the top rim as the soil will settle.