Your mulch gradually decomposes over time, and when it looks thin and I can see the ground, I add more. It has been a year and a half on one of my gardens mulched with shredded redwood and it needs more now. Different mulches last varying times. For my pots the only thing that prevents girdling of the roots is potting up to a larger size. Al

The Air pruning pots do work! No circling of roots. When the root hits the air, it dies, pruning the tip, and then it sprouts feeders so you get maximum use of your soil. Try one of each and then in a year, see which plant is root bound and which plant has a huge full root ball. There is a major difference!