Update: Ecosystems in a Jar!

Some of you have asked about caring for your child's ecosystem in a jar. They are designed to be self-contained, so you shouldn't need to water them often. I suggest checking on them every week or two by opening the jar and making sure the soil is moist and the plants look healthy. You also should be able to observe water droplets on the inside of the jar, which indicates there is sufficient water inside.

A note: If your child's ecosystem contains a plant that looks like the photo below, you may need to remove it from the jar. It seems to be ill-suited to the very moist environment and will start to rot. Sorry about that! Let me know if your child needs a replacement plant.