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Buy a bag of foam packing peanuts instead (available at office supply stores). Fill the pot one-third to one-half full of peanuts, cover with landscape fabric and then add soil. This cuts the weight and saves money, since peanuts cost less than good potting soil. However, a smaller amount of soil means more frequent watering. To slow evaporation, cover the soil with wood mulch.
Cut the bottom off a plastic pot to contain invasive plants & bury in the ground. I have been doing this for a few years & works great for containing plants that tend to spread, but that I still want to plant in the garden. This also works good for planting a plant in an area that tends to get filled with roots etc. from other plants. I will use a larger pot so that the plant can spread it's roots and grow deeper roots, but keeps other tree roots from choking out the one I planted.
20 Insanely Clever Gardening Tips And Ideas...some really really good ideas, though a few might need some tweaking.