First, find a glass container. For a closed terrarium, any glass container with a removable lid will work. You can order one or find one around the house. It could be a rectangular glass box with a top or a rounded jar with a stopper. A Mason jar, either upright or on its side. A covered fishbowl. A cookie or candy jar. You can also use plastic if it’s clear and resists fogging.

Lay down a base. Use rocks, plain or colored gravel, seaglass or other decoratives. This is your drainage layer. It should be about an inch deep, but that can vary depending on the size and shape of your container. The finished product will need enough “headroom” for your little garden. The base layer doesn’t have to be flat; you may shape it to create peaks and valleys.

Some sources recommend a ½ inch layer of charcoal next as a water filtrate.

Create a barrier for your soil with sphagnum or sheet moss. Soak it briefly, squeeze out the water and mold it into place.

Add about two inches of soil. Common potting soil is good for most plants. If your gravel layer is flat your can shape this to make miniature hills and valleys.

Now you’re ready to plant. Use slow growing vegetation and dwarfs. Peperomia, ferns (maidenhead, button ferns), pilea and dwarf palms are good choices, as well as miniature coleus, violets, begonias. There are suitable lichens and mosses.

As for maintenance, there’s not much. After an initial watering, you have only to keep it moist. For a closed system, which recycles water, a light mist every few weeks is adequate. Once a week, briefly remove the cover to rebalance the air. Trim plants to keep them small. Terrariums do best in indirect sunlight. The glass can magnify direct rays.