The containers you choose to use should be clean (rinsed with a few drops bleach in water and dried upside down) and bone dry. If you get impatient and try to work with a container with moisture still in it clean up will be more difficult later. Other than that- use your imagination! Use wine bottles, vases, tiny bottles, bowls, containers with lids- anything! If the glass vessel has an open top think of how you may want to cover it sometimes to create a moisture lock. Sheets of plexiglass, plant dishes and even dishware plates can work.
Mix two parts potting mix with one part sand to ensure proper drainage. If your terrarium is on the small side (decorative bottle rather than aquarium), you may want to increase the amount of sand and decrease the amount of soil. Add distilled water to make damp but it is easier to transfer to terrarium when it is dry. Remember - you can always add more water to your final terrarium but it is difficult to remove! Make sure you have enough of the mixture to fill 1/4 to 1/3 of each terrarium you plan to make.
Once you have layered your dirt into the terrarium you'll want to mist down the soil with water (distilled is best). Soil will need to remain damp throughout the life of your terrarium to support your plant growth.
Pebbles, small rocks or small pieces of glass can all be used for the rock layer in your terrarium. Get creative but make sure all items can fit down the neck of your glass container- a piece of glass stuck halfway down can pose a problem for removal!
Charcoal is an essential element in terrarium making to ensure the ecosystem stays "sweet." You can buy activated charcoal at any aquarium supply location. The charcoal is often "dusty" so I normally pour a small amount on a paper towel to catch some of the dust. If you pour charcoal directly from the bag into your container the dust will cling to the sides of the container- and find any moisture that may be in the bottle.
Damp Spaghnum Moss
Soak some spaghnum moss over night in tap water and squeeze dry. The spaghnum moss will act as a filter between your soil layers and charcoal, and is optional. Tear the pieces into sizes about the diameter of your container opening.
Decorative items are of course optional. Be choosy- I think the kitsch pieces can really detract from the beauty of the plants. I like to use glass marbles and tumbled glass. Other options are small sculptures, twigs etc. Be wary of introducing an item from nature (like a lichen twig, etc.) that may introduce foreign bacteria into the system. If you can- incubate the item for a while and observe if mold grows.
Don't be afraid to use juvenile plants in your container. You will find that they will grow fast in the ideal condition of a terrarium so I always try to err on the side of caution and use plants sparingly in a young terrarium. Also remember that it is always easy to add moss and small plants to the terrarium later, once it has settled a bit.
I also strongly recommend that you quarantine plants from nurseries or nature for a period of a week or more. Any live stow-aways will surface, you can observe if the plant takes to terrarium conditions and if the plant is diseased you can dispose of it without fishing it out of a small terrarium. Some how-tos may suggest rinsing the plant with a little bleach or dish soap first as well. This is your call- I find a normal water rinse on foliage before a one-week incubation is normally fine. The one exception is moss! You must wash your moss (See post on how to wash moss and why here).
Tools I absolutely recommend and will use in this demo are: bamboo skewers, several sheets of clean white paper, distilled water in spray bottle, spoon, serrated knife and scissors. These are the bare basics. Other suggested items you might not have around the house are: large tweezers (from surgical supply store or craft supply), pipe cleaners taped to bamboo skewers to use to clean inside of bottle, and a small piece of foam stuck on a bamboo skewer to use as a tamper. I'll delve more into tools and how to make them in another post.
This is the first post in my series "How to Make a Terrarium"
Next Post: Adding Soil Layers