"Generally, a plant is ready for transplanting when most of the soil in the pot is completely full of roots, top to bottom, probably the third or fourth year it has spent in your house. Many plants prefer to stay in a crowded pot and actually grow better in this environment. Find out if your plant is a crowded root lover or a space hog before transplanting.
To ensure transplant success, transplanting should be done in spring while the outdoor light is increasing, this will give the plant time to root in and get comfortable before winter. Pick a pot that is two inches larger than the pot your plant was growing in, the plant will appreciate the new space but will still feel anchored enough to start growing. This is also a good time to fertilize your plants and do any trimming or pruning required."
—Audrey Flanders owner of Audrey's Little Shop of Plants