The few needs of terrariums allow them to be all but forgotten, then noticed in some idle instant between the bustle of tasks that occupy our lives, giving sudden delight. Terrariums are one of those pleasant distractions that remind us life isn’t about meeting goals. Every terrarium is a perpetual experiment. Plants react in surprising ways to the humid environment. Roots grow into the air and along the glass as well as in the soil. Flowers grow and hang on their stalks, untouched by bee or gust of breeze. Terrariums remind us to wonder.
Gravel, Sand, and Dirt
My terrariums contain three ingredients: fine gravel or sand, loamy dirt, and moss and plants. I can add as much gravel or sand as I want in decorative patterns, or so thin a layer that it almost vanishes under the moss. I keep the soil to a minimum, just enough to cover the roots, and never use dried sphagnum, peat, or any other non-living material that can grow mold. There is no need for a filter between gravel or sand and soil as long as the gravel or sand is fine enough.
I use water from my pond to wet the terrarium when I make it, which is all the fertilizer it will need until it wants water again, which won’t be for months. You can use any dilute liquid fertilizer.
Choose plants that favor bright indirect light and humid conditions. Most small jungle plants work well. If you don’t mind turning the terrarium and trimming the plants frequently (you can plant the trimmings right back in the soil, or start another terrarium) there are many options. Easy flowering plants include: begonias, impatiens and peace lilies; while the gorgeous leaves of polka dot plants and coleus can spice up the terrarium between blooms.
If you would rather have a carefree terrarium that looks good all the time, choose specimens that tend to grow slowly and stay small. African violets and miniature orchids are good options, as are delicate species of ferns like the maidenhair fern. Zamioculcas, ivy, ficus, and azalea have all done well in my terrariums without taking over. Even if you use mosses alone, you are likely to get some volunteer ferns.
Terrariums thrive in bright indirect light all day. Up to an hour of direct morning or late afternoon sun brightens the green of the mosses and gives robustness to plants that tend to grow spindly, but direct light can be dangerous, causing leaf burn and overheating of the glass environment.
Watch young leaves and the tips of the mosses and move into less light if you see yellowing or burning. If you would rather have complete control of your little world, use a full spectrum grow light, and carefully monitor how close to the light the terrarium is to avoid burning. Generally, two to three feet is about right.
If plants appear dry, add a mist of water every day until they seem healthy. Er on the side of dry. More plants die of too much moisture than too little in a terrarium.
…and leave it alone! Carefully monitor, but resist the urge to adjust things unless there are clear signs that a change is needed.
Terrariums are kind of like a chicken roasting in the oven: there is a climate, humidity and temperature, that can be disturbed by too much introduction of outside environment.
When finally you open your terrarium to trim plants or perhaps wipe the glass if it becomes dirty with snail tracks, it should smell like rich dirt after a rain.
I hope you enjoy making terrariums as much as I do. I have found few hobbies that combine my love of art and plants as affordably and easily, or that offer so much magic for the effort. Don’t hesitate to contact me with any questions at all! I absolutely love talking about terrariums.