PVC Garden "Pots" -- On b organic with michele beschen episode #212, a CSA had lots of unique planting methods that were inexpensive, deer- & weed-proof, AND accessible to someone in a wheelchair. PVC pipe (10’ lengths) cut into 3 equal pieces, secured in the ground with a piece of rebar, and filled it with soil were used to plant all sorts of vegetables and plants, 1 plant per "pot". Each plant took just one cup of water per day to thrive! Here is a similar idea on a DOT government website.
Also on these boards
Smart ~ cut the bottom off a plastic pot to contain invasive plants & bury in the ground; works great for containing plants that tend to spread. This also works good for planting a plant in an area that tends to get filled with roots etc. from other plants. Use a larger pot so that the plant can spread its roots and grow deeper roots, but keeps other tree roots from choking out the one planted.
Use PVC pipe to hold sprinkler spikes....or path lights
Disney world does this! Lowes sells the 4 to 6" round PVC pipe with holes already drilled. Purchase an end cap, fill with rock, soil, and plant. I will often put these in the center of a very large pot to stabilize, and add amazing height and color to a container that has trailing plants (no end cap or rock needed if you are placing in a container)