However, if you have a large container (better for keeping the plants moist in the heat), you may want to offset the cost of the soil by filling the bottom with lightweight items like plastic water bottles, crushed soda cans, crushed milk jugs, or plastic take-out containers. Steer clear of foam packing peanuts or containers, as they are very hard to dispose of after the roots have grown into them and they break up into lots of smaller pieces.