I think I may have almost killed a tree because I did not transplant it to a larger container. When does one know to transplant to a larger container? I need to do it for a bush that clearly seems to need a new pot. Any advice would be appreciated for this novice. My plants are on my roof deck that has lots of sunlight in the northeast U.S. They remain there throughout the winter. Thanks in advance.
For most container grown plants, they need to be repotted into a larger pot or root pruned and placed into the same container every few years. Usually before they become too rootbound. When you remove the plant from the old pot, you may have to loosen or even carefully slice the root ball before you place it into the new pot. You could mix alittle compost in with your potting soil. Apply some good food and water in well(unless you are potting cactus).
When the roots of your plant take up the entire pot, it is time to give your tree a small root pruning and pot it up. Though, the best time to do this is when the tree is dormant. So, fall would be the best time.