How to Make a Terrarium—and Help Your Miniature Ecosystem Thrive

Even if you don't have much of a green thumb, terrariums act as small, self-sustaining ecosystems all on their own. They're a great place to grow plants that thrive in high humidity and low light, like tropical ferns, mosses, selaginella, peperomia, cryptanthus, and air plants. While it may seem like an intricate process to replicate these miniature worlds, it's as simple as layering pebbles, horticultural charcoal, and potting soil together in a glass container.

Related: 8 Houseplants That Thrive in Low Light

First, choose a good container. We used kitchen canisters, which are readily available and inexpensive; their tight-fitting lids capture the condensation the plants require to thrive. Keep in mind, however, that not all containers are suited for being repurposed into terrariums. Ideally, a closed container with a lid will encourage the humidity that helps your plants thrive. Search your attic, basement, and cupboards for unique vessels, like clear soup tureens, kitchen jars, and empty bottles. Whatever you choose, be sure that it is smooth, clear glass. "Colored glass will block the sunlight your plants need to thrive," says Todd Carr, gardener and founder of Hort and Pott.

Now that you've selected your container, you're ready to build your terrarium. When creating the drainage base of pebbles, avoid placing the structure in haphazardly. For precision and even distribution, use a pastry bag with no tip to add fine soil or gravel to your terrarium.

1. Deposit a base of pebbles or gravel about 1 inch thick (this is a must for drainage).
2. Add a thin layer of horticultural charcoal.
3. Add a layer of potting soil.
4. Nestle your selection of plants neatly into the soil so the roots are covered and any leaves, petals, and stems do not touch the glass. 
5. Add other touches if you'd like, like figurines and uniquely shaped rocks.

While they're relatively easy to make, terrariums require some basic care to ensure the plants inside them thrive. Ensure you're giving them adequate water and light while you display the tiny ecosystems throughout your home.

The worst thing you can do is deluge your plants with water, so you'll want to be careful when giving them a drink. Just spritz twice with water and place the lid on the jar, making sure no water is pooling at the bottom. Terrariums act like tiny greenhouses, resulting in condensation on the inner walls. If you find that too much condensation forms, give the terrarium a little less light or remove the top for two hours.

Most terrariums prefer being kept in a spot with diffused light, such as by a south-facing window. Never place your terrarium in direct, bright sunlight; the afternoon heat can damage the foliage.

Terrariums like humidity. Keeping the terrarium closed is what traps the humidity and keeps your plants happy. Therefore, a little ingenuity is called for if you're using a container without a lid: "If there is no lid on your terrarium, you can use a glass plate on the top," Carr says. "Or if it's a narrow-necked bottle, use a lightbulb to block the opening and create extra humidity."

Clean the inside once you begin to see water spots or algae buildup—this typically occurs once a week. Reaching the corners of a container isn't always easy, which is why you should have a stash of makeshift tools, like long-handled tweezers and scissors, handy.

You can use these tools to remove debris from hard-to-reach your terrarium. "Use long-handled tweezers and scissors to either pick up dead leaves or prune leaves off the plant or edge of the glass," Carr says. "Chopsticks can work as well."

When even tweezers won't help you hit those out-of-reach corners, a wire hanger will work. "Use a wire hanger to create a little hook or loop to move leaves and plants out of the way to gain access and see what you're maintaining beneath," says Carr.

Wire a small piece of sponge to a sturdy structure (a chopstick, a wooden spoon, or thin bamboo will work) with floral wire. Use the sponge to wipe the inside of your glass terrarium clean.