[header] How to clean a planter [title] Understand why it's important to clean your planter. [step] Disease can be transmitted between plants if you don't clean out a planter, even if you replace the soil in it. Disease spores hide in plant matter and can remain in soil for many years. 
That's why it's important to clear all disease-carrying material out of planters between uses. [substeps] Porous planters, such as wood and terracotta, will harbor disease especially well.