In one previous post I wrote about tillandsia care, and in another about constructing a terrarium. Since writing these two posts, I have noticed that one particular air plant terrarium here in the Carrboro store does extremely well. Every plant we put in there takes off until someone comes along to purchase it. Since noticing this phenomenon, I have begun mimicking the layers in other terrariums and have had similar success each time. In this post, I want to discuss this particular terrarium design in a bit more detail, and share the process for making your own air plant terrarium that does especially well. There are three layers involved in this terrarium method: the base, the moss, and the decorative.
As with all terrariums, the bottom layer is for drainage. This layer prevents organic material from rotting, and consists of inorganic material: sand, stones, seashells, marbles, etc. With tillandsia, this layer also keeps them from sitting in water, which I have personally found to yield a quick death to these little bromeliaceae. For my terrariums, I tend towards stones, but have used a plethora of items. For the air plant terrarium, use a very, very thin layer, about ½ to ¼ inch, since the containers are smaller, the glass is usually thinner, and we really want the focus to be on the plants. While this layer catches any extra moisture, there should not be too much excess moisture in an air plant terrarium, which is why this layer can be so thin.
Next, add a full layer of moss to hold some extra moisture. This part is fun; use whatever looks pretty to you. Just keep in mind that you will mostly only see it from the sides. I have used sheet moss, reindeer moss (actually a lichen), sphagnum moss, and some strange items I found at a craft store in a DIY potpourri package. It seems strange to have one layer to retain extra moisture directly on top of another to keep it away, but this moss layer holds humidity tillandsia need. In my experience, when I just have a drainage layer, the water evaporates much too quickly due to the plants’ airflow requirements, and eventually I found dead tillandsia. It was a much slower death than drowning, but fatal nonetheless. So this mossy layer provides extra humidity to compensate for the extra air flow. Well, that, and it also looks wonderful.
In my experience, having just these two layers is not quite enough to keep air plants healthy and thriving. The extra humidity in the moss layer, held directly against little tillandsia, can once again lead to a horribly tragic rot. Solution: Add another drainage layer. Now this is a little more complicated than just adding another ¼ inch of pebbles to cover the moss. I still want to be able to see most of that beautifully decorative moss I put in the terrarium, and I want any surface not directly touching my plants to add as much humidity as possible. To achieve these aesthetic and practical goals, I add stones to the area directly under where I plan to put my tillandsia. The stones prevent the plants from directly touching the moss, allow the moss to be seen and do its job of providing humidity to the terrarium, and add another pretty, decorative element. Again, any inorganic material should work here, just like in the base drainage layer. I even have broken terra cotta pots in one of mine at home. If the very top of the moss touches the tillandsia, it should be okay, as long as it is only a little bit here and there.
Once you have all three layers set, place your plants on the top-most drainage items, adjust until you have the placement you want, and voila: one incredibly successful and beautiful air plant terrarium.