Q. How do I make a moss terrarium?
Thank you for your question about moss gardening. If kept indoors, terrariums with moss require more light than you might realize: bright light but not direct sun. They definitely need a fair amount of relatively strong, natural light, or more regular artificial light from fluorescent or LED grow lights.
Indoors, a large terrarium featuring moss should be kept reasonably close to a window. Humidity is important. Enclosed in a terrarium with a top (bell jar, or tightly covered cookie jar) is one way to grow it. But, air exchange is needed also, by removing the cover occasionally, or leaving a space between the lid and container can help.
Moss from a moss farm where it has been nursery grown and propagated is the best moss for successful growing. There are tropical mosses, selaginella, occasionally called club mosses or spike mosses. Your moss may go dormant btw; but possibly can be used as a propagation material to grow more moss, unusual but can be done.
So it sounds like this is not the easiest garden to keep going forever, here’s more: http://www.mossandstonegardens.com/blog/one-tall-dish-baby/
What’s needed for the glass container terrarium garden:
Start with about an inch of gravel. 1/8-inch crushed type (from fish store). Sprinkle charcoal over the gravel to keep soil sweet. Add soil mixture, a couple of inches. Note: make sure the clumps of moss are pressed firmly into wet soil on top to make a good bond - moss does not do well with air space between it and the soil. Mosses prefer growing on firmly packed acidic soils with a pH between 5.0 and 5.5.
Courtesy of NYBG Plant Information Service