This is an awesome way to grow some vegetables if you have very limited space and where it is very dry. Desertification shows how to make these bottle towers so you can still have a garden for fresh produce. They even show how you can add sand to the bottle where water is added to filter out any material that may be in the water. This is a really smart idea for small spaces especially in a dry area.
http://desertification.wordpress.com/2011/10/17/combating-malnutrition-in-the-drylands-how-to-build-a-bottle-tower-for-container-gardening-willem-van-cotthem/
