Here are a couple terrariums we made out of pretzel jars (WD-40 works really well at getting the label/glue off).
There are instructions all over the internet for making a terrarium. Basically, put down a layer of pea gravel, some aquarium charcoal, then the dirt. Choose a small plant and add some water. Finally, close it up.
Place the terrarium out of direct sunlight. You need to monitor the moisture, and open the lid if there is too much. These are not doing that great anymore, but it has been 8 or 9 months since we made them.
Close-up of the gravel, charcoal, dirt layers
Since this one was horizontal, we also made the little stand for it. And no, the creatures are not real.
Any more ideas for old pretzel jars? Leave a comment...