We do not recommend adding casters/wheels to the bottom of our Planters. Each of our Planters has a double-walled design creating our water reservoir feature; the plastic walls are about 1/8” thick and the section directly beneath the floor of the planter is hollow so that it may be filled with water. Drilling holes in the bottom would ruin the water reservoir feature and there would be nothing to drill into to keep the casters in place.
Please note making any structural changes to the Planters would also void the 15-year warranty offered with our products.
A great solution for making your heavy planters mobile would be to create a platform for them to sit on and attaching the casters to the bottom of the platform. A platform can be made from a piece of pressure-treated plywood cut so that it is just slightly smaller than the base of your planter.
Another handy idea would be to add a lightweight Filler which would make your Planter lighter and easier to move without any additional hardware or modifications.
Alternatively here are a couple of planter caddies we have found available online that would work great for our planters!