I've been known to put rocks in the pots to add weight. Especially on plants with shallow root systems like tall Sansevierias where they don't need all the pot space. I've used rebar, but then discovered I couldn't pull it up after I got it in the ground. I had to use the pick to dig it out, so it wasn't a satisfactory solution. I tend to rearrange things too often
. Some people think that's funny/odd, but really some plants grow too large, or they seem to need more light or they get past their peak in a visible spot when another is reaching peak. They get switched around pretty often.