Here are the things you need in order to make one:
- A closed glass container - I would suggest a taller one to give the plants room to grow
- Rocks or glass beads - if you don't have any rocks around the house or garden, you can find decorative ones in craft or dollar stores for pretty cheap
- Activated charcoal or carbon - I found some in the aquarium section at the local pet store
- Potting soil
- Moss - I used sphagnum peat moss that I bought at the home improvement store, but optimally you'd want live moss that you could gather from outside or that you could get at a garden centre
- Small plants - ones that do well in shadier areas would be better if you'll be keeping your terrarium in a low-light location
To build the terrarium, start by washing the container well. Put the rocks or glass beads in the bottom of the container and layer the activated carbon on top in order to filter the water so it doesn't get stagnant in the closed container. If you don't want the soil mixing in with the stones, then layer the moss on top of the rocks. Pour in a layer of potting soil - enough to allow the plants' roots to grow. I layered some big glass beads around the container before I put the soil in for more of a decorative touch.
Next, put the plants in place and pat the soil down firmly around them so that they are well supported. I think the terrarium looks best if you include plants of different heights. I also tried to get a plant that would provide some coverage across the soil as it grows. I would probably have layered some live moss on the soil as well, but there's still snow on the ground and I couldn't find any at the garden centre. I put some little rocks on top of the soil for decoration, but you can use your creativity and put in whatever you'd like.
Lastly, pour some water in the terrarium and close the top. You should check on the humidity in the terrarium from time to time. If it's too wet, leave the top open for a while so that some moisture can evaporate. If it looks too dry, add a bit more water.
Next time, I'll use a taller container or make sure that the plants I get won't grow too much. I've already had to trim the ones I used and it's only been a couple of weeks since I planted them. There wasn't a lot of selection at the garden centre since it's still winter, but I'll look again in the spring for little plants and make a few more terrariums for the house. I think the plants look so much cuter in their glass containers than in the terra cotta pots that I usually use. So pretty!