The terrarium pictured above is my attempt to revive a plant which seemed to never get enough water, no matter how often or how much it was watered. The problem appeared to be with the original commercial soil mixture in which it was planted. That mixture allowed water to seep right through it and down to the bottom of the container where it quickly evaporated.
In order to revive the plant, and to make a conversational item placed on a side table in the living area of our home, I repotted the pepperomia large-leafed plant in a wide-mouthed glass snifter. I also transplanted some ground cover from our back yard which was sprouting back from the winter. The plant(s) have now been thriving in their new environment for about two weeks.
The instructions of how I prepared the terrarium are listed below, as well as the link to the site which was investigated.
Creating your terrarium: Before you begin construction, get all of your tools, materials, plants, and of course your container, together in one convenient place. Your planting foundation will consist of four layers.
The bottom layer is for drainage, and consists of pea gravel, pebbles, or very coarse sand.
Proper drainage is essential to ensure that the soil doesn't become over-saturated, which may lead to root rot, and the death of your plants.
Depending on the size of your container, you will want to spread at least an inch of drainage material evenly across the entire bottom of your terrarium. For large or deep containers, up to 3 inches of material may be used.
On top of the drainage layer, it is a good idea to spread a thin layer of activated charcoal (like you would use in your aquarium filter).
This layer will help to clean the air of the fumes caused when the organic materials begin to decompose.
The third layer is a thin cover of sphagnum moss, spread over the first two layers.
The purpose of this, is to prevent the soil from sifting down into the drainage layer, which would render it useless.
The final level is that of your soil. Many garden centers sell a potting mix specifically for terrariums. In reality, all that you normally get for the extra money, is sand added to their regular potting mix. You may choose a pre-mixed terrarium soil, or, if you prefer, just add one part coarse builders sand, and one part leaf mold (or humus) to each two parts of your usual mix. Never use beach sand in any potting mix! Do not add any fertilizer to the potting mix. It already has enough nutrients to last a long time. Too much will cause the plants to out grow their surroundings, much too quickly.