Step 1: Materials
Glass jar with lid or cork
Pebbles or gravel
Spoon or funnel
Water spritzer bottle
Some notes on finding supplies
Activated Charcoal: Your best bet for finding activated charcoal is an aquarium or pet supply store. They sell this charcoal in bulk packages. This is the type of charcoal used in Brita filters and air filter masks as well. You only need a few tablespoons of the stuff for one moss garden.
Peat Moss and Potting Soil: These are common and can be found in at most garden centres.
Pebbles: You can find pebbles on the ground, or you can buy them in a store. Aquarium stores sell pea gravel that is the perfect size. The stones should be quite small, about the size of lentils or raisins. You need enough pebbles to create a solid layer in the bottom of your container. Wash your pebbles well before using them.
Step 2: Find a Bottle
Once you start looking, you will see bottles everywhere. You can recycle old jars or bottles from your house - salt shakers or clear glass spice jars work well. I like to find bottles in thrift stores or garage sales, or rescue them from the garbage.
I recommend a wide-mouthed container (such as a canning jar or spice jar) to start with - it's a lot easier than one with a narrow neck.
The bottles that work best are ones that have a tight fitting lid. This helps to keep moisture inside the container.
Step 3: Find Some Moss
Look for places that are moist and slightly shady. I avoid moss growing on trees. I also avoid moss from sensitive areas like protected parks or by streams. Once I really started looking, I noticed that plenty of moss grows right by the sidewalk, in that grassy strip between the sidewalk and the road. It can be hard to spot sometimes, because it is often mixed with grass. This roadside moss is often quite hardy because it is already growing in a tough environment.
If you know someone with a shady backyard, try looking there. If you're really having trouble, try talking to some local naturalists, or do some moss research. There is an incredible book called Gathering Moss by Robin Wall Kimmerer that can help you understand more about the different types of moss and where they might be found.
Step 4: Collect Moss
As a rule of thumb, I only harvest 25% or less of the moss in one area. You really don't need a large amount of moss - just enough to cover the bottom of your glass container.
When collecting moss, I place it in a plastic bag to help keep it moist. If you aren't using your collected moss right away, you can spritz it with water and store it in the fridge in a tupperware-type container.
Step 5: First Layer: Pebbles
When your bottle garden is complete, the pebbles will provide a place for water drainage.
Step 6: Second Layer: Charcoal
The charcoal acts as a filter, grabbing impurities out of the water as it drains through to the pebbles.
Step 7: Third Layer: Peat Moss
For anyone unfamiliar with peat moss, it doesn't actually look like living moss. Peat moss looks a bit like soil, but it is made from partially decomposed sphagnum moss. A layer of peat moss holds water and helps to prevent the soil nutrients from leaching through to the bottom of the container.
Step 8: Fourth Layer: Soil
Half an inch to one inch should be enough. If the soil is dry, spritz it with some water from the spray bottle.
Step 9: Final Layer: Moss!
If you are using a wide mouthed jar, gently tear off a piece of moss just a little bit smaller than the bottom of your jar. Push it into the jar so the bottom of the moss mat is touching the soil. Spritz generously with water.
If you are using a narrow-necked bottle, tear off a piece of moss that will fit through the bottle neck. Using chopsticks or something similar, push the moss through the bottle neck and into the bottom of the bottle. Make sure the moss lands right side up. You can probably flip it over with the chopstick if it lands upside-down. Do the same with other small pieces of moss until the soil is completely covered in moss. Using the stick, lightly tamp down each piece of moss to keep it in place. Spritz the bottle with a little water.
Step 10: Finishing Touches
Keep an eye on your moss garden. If the lid is loose or has holes in it, spritz your garden with water once in a while. If it seals really tightly, you probably won't have to water it, but the moss might grow very fast. When the moss starts getting too tall for the bottle, 'mow' it with a pair of scissors.