I have a plastic, rectangular planter with a variety of plants. I recently added a new plant to an empty spot, and found that the region was already thick with root fibers from the other plants in the planter, and starting to cluster thickly around the edges.
I saw the question about pruning rootbound plants, and don't want my planter to end up like that. But, since this is a planter, i can't just pull out the whole thing and prune the roots. How do I keep the roots of my plants from becoming overgrown and fighting with each other in a planter?