I love big containers but I don't love hauling them during cold season. I used to stuff the bottom with packing peanuts but if I ever replanted pots, the peanuts made a mess. These days I've found that chunky styrofoam used for appliance packing or swimming pool noodles ($1 @ $ General) are much better fillers.

First I cut a small piece of vinyl window screen ($6/roll at hardware store) and place on top of drain hole(s) to slow down soil erosion.

I stuff pot with styrofoam chunks or in this case, noodles, anywhere from 1/3 to 1/2 of pot, depending on what I'm planting.

I place another piece of window screen on top of styrofoam and fill with dirt.

I plant my pretties. In this case it is a tall canna, which is why I only filled 1/3 of pot with/ styrofoam. Want a lighter pot but not where it becomes too top heavy and gets knocked off by wind, pets, etc.

If you still find that fiddling with chucks of styrofoam is too messy, you can stuff a knee high hose w/the material and place in your pot. That way, if you need to redo pot, the process is reduced to 2 simple steps: 1) dump dirt, 2) dump 1 bag of styrofoam.

Excellent! Empty bottles with cap on can also fill excess space.

Bottles have not worked for me as they're not stable. Styrofoam seems to mold against itself. I hope somebody that uses bottles post here.

I use bottles but not the kind that is used for water bottles that are sold in bulk at the grocery store. You know the kind that slowly collapses as you are trying to hold onto it while drinking water. I use the plastic bottles that tomato juice and other specialty drinks come in; they are usually of a thicker plastic that doesn't collapse easily. They also tend to be bigger than a regular 8-12 oz water bottle so can take up more room in an oversized planter. I put them right side up and upside down at the same time or even lay them down depending on how much depth in planting I need.

I have at home a couple pots that are 25 inches in diameter and use the "filler" to save on the amount of soil needed to fill the pot. So no matter how many bottles lighten the load to move a pot, a planter tray on wheels comes in handy to move the pots around regardless of what season it is.