Container gardening is an alternative for people living in apartments or others areas with limited space. Raised containers are also convenient for those who find kneeling and stooping difficult. Filling large pots with soil can be expensive, and those big pots are heavy when filled with dirt. Partially filling the pots with plastic bottles addresses those concerns, while adding an extra kind of "green" to your garden.
By filling the bottom of your pot with old plastic soda bottles, you are able to use considerably less potting soil than you would otherwise. Depending on the plants you are growing, you can fill the large flowerpots half to two-thirds with capped soda bottles, water bottles or other containers of similar sizes. In addition, because you are using less soil, you lower the risks of spreading plant diseases found in unsterilised soil and you may need less plant food or fertiliser, since less will be lost to the soil itself.
A large flowerpot filled with quality potting soil is heavy and difficult to move around, especially if you are using terracotta or ceramic planters. Even setting the pots on saucers with casters may not allow some gardeners to move those dirt-filled pots, and you may find just rotating the container for even light exposure nearly impossible, depending on its size. By eliminating half or more of the dirt, you cut the weight significantly, making the pots much easier to relocate when necessary.
As long as you remember to leave the caps on the bottles, partially filling the pots with soda bottles will provide the needed drainage arrangements. If you fill the area containing the bottles with water, you may also find that you need to water your container garden less often, since the plastic-filled section serves the same purpose as the reservoirs of speciality self-watering pots. Push the end of your garden hose blow the soil level, into the lower section and fill it with water. Even in hot, dry climates, you may be able to water once a week, rather than every other day.
Using plastic bottles to fill your plant containers allows you to "go green" and help the environment in several different ways. Repurposing the bottles means that they don't enter a landfill, easing the concerns related to an overload of garbage that does not break down quickly. By holding the water in the pot, the bottles also contribute to resource conservation, which is especially important during hot summer months or droughts.