I just ran a test in which I determined whether planters and pots were helpful in having plants produce fruit faster. I timed an apple tree's growth to adulthood, and from adulthood to first harvest, in planters, pots, and straight in the ground. I found that the planters and pots didn't change the time of the plant to reach adulthood, and shaved off a very small amount of time (0.76%, or a little under half an hour) from adulthood until first harvest.