Closed Terrariums: Indoor Gardens Under Glass.
As a flat dweller in Central London, my gardening has been limited to four – dare I say spectacular – window boxes, an occasional potted plant, and more recently, terrariums.
Closed terrariums are tiny indoor gardens under glass and are well-suited to moisture-loving plants like ferns, Friendship plants (Pilea involucrata), and Nerve plants (Fittonia). Open terrariums (i.e., not enclosed or covered) are better suited to more drought-tolerant plants like cacti and other succulents.
Step-by-Step Guide to Making Your Own Closed Terrarium
Here’s an easy six-step guide to a Do-It-Yourself closed terrarium. (Please see our DIY guide for open terrariums if you’re interested in drought-tolerant plants. Open Terrariums.)
Materials Needed:
To make your closed terrarium you’ll need the following:
- A closable or covered vessel like a clear-glass cookie jar or even a cloche
- Pebbles and / or gravel
- Activated charcoal
- Potting soil
- Small moisture-loving plants – For my closed terrarium, I chose, Soleirolia soleirolii (Baby’s Tears), Muehlenbeckia (Wire Vine), and Dryopteris (Wood fern), which will overtake a terrarium unless pruned regularly. Fittonia (Nerve plant), Peperomia (Radiator Plant), and Pilea (Chinese Money plant) also work well in closed terrariums.
Step 1. Place a 1/2-inch to 1-inch layer of pebbles / gravel on the bottom of your container. I prefer a mixture of small pebbles and gravel as I believe it provides better drainage than just gravel or pebbles.
Step 2. Add a 1/2-inch to 1-inch layer of activated charcoal to aid drainage and help filter the air.
Step 3. Cover the activated charcoal with a 1-inch to 2-inch layer of potting soil.
Step 4. Using an old spoon, dig a small hole in the potting soil for each plant. Leave some space around each plant to allow air to circulate.
Step 5. Place your plants in the prepared holes and firmly pat the soil around the roots.
Step 6. To help the plants recover from the shock of transplanting, lightly water them and then close the container.
Caring For Your Terrarium
Closed terrariums require high light but no direct sunlight since the glass jar intensifies the sun’s rays and will burn your plants.
Too much moisture can also be a problem for mold growth and root rot, so water your closed terrarium infrequently. Remember, you’ve created a closed environment and moisture will naturally recirculate in such an environment. Start with a very small amount of water every week (think thimble size). In the winter, plants generally need less water so I only water my closed terrariums once every two weeks.
Keep an eye out for condensation on the inside of the glass container. If you notice large drops of water forming, open the container for a while to let moisture escape. If the soil appears to be dry, you may wish to use a spray mister between waterings. Water requirements will vary depending on the number and types of plants you’ve chosen and the ambient temperature in your home.
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