It just so happens that you may end up buying a concrete urn and if you do, you may want to know how to clean it properly. If it already has soil inside of it, go ahead and use a spade to shovel it out of the urn. Once you have ridden the urn of all the soil, grab your garden hose and fill up a clean bucket with water. From there, go ahead and add around two to three tablespoons of mild dish detergent. Also, grab a scrubbing brush as this is the tool you will use to clean the inside of it.
As you would anything else, take the brush and dip it into your solution of water and begin to clean the inside while rinsing it out thoroughly. Once you are sure the interior is clean enough, rinse it out one last time. Now, do the same to the outside of the urn and you should be golden.