Enclosed and Open Terrariums

A terrarium is a miniature world in or under glass popularized by Dr. Nathaniel Ward. While traveling between Europe and the tropics, Dr. Ward collected insect specimens in sealed glass bottles. One day he came across an old bottle collected months before. The insects were dead, but to his surprise, a tiny fern and some grass were growing in a soil at the bottom of the bottle. He hypothesized that plants could grow under glass. The fern and grass lived in that sealed bottle for about 4 years. After this, Dr. Ward had a glass case built and successfully grew ferns inside it. With his invention of the Wardian Case, he helped merchants bring tropical plants across the sea. In previous years, 19 out of 20 plants would perish during the long journey. After the invention of his Wardian Case, 19 out of 20 plants survived the journey.

Fish Bowl Terrarium

To make your own terrarium, gather the needed materials of a clear glass or plastic container, plants, gravel, activated charcoal, soil, and of course, some fun accessories! And last but most important, choose the place you to keep your terrarium. Terrariums do best in low to medium light. Never place a terrarium directly in a sunbeam. Direct sunlight causes the greenhouse effect and will slowly cook your plants.

Step 1: Containers can be found around your house, your grandma’s house, thrift stores, garage sales, craft stores, etc. Here’s a quick run-down on containers:

• Enclosed Terrariums: have a lid and are very low maintenance. Once planted leave them alone for many months.
• Open Terrariums: have no lid and are low maintenance, but soil dries out faster than enclosed terrariums.

Inexpensive Containers

To make an inexpensive terrarium, use a spaghetti or pickle jar, or a plastic soda bottle. To get rid of any funky odors, set the container in the sun for a few hours. If the label isn’t easily removed, put the it in a sink full of warm, soapy water for 10 minutes. Then scratch the label off with a fingernail. Use a scrub brush to remove any remaining glue. Make sure to wash the inside of your container with warm, mild soapy water.

Rhizotomous begonia, Parlor Palm and Button Fern

Step 2: Plants can be found in lots of places, including, of course, your grandma’s house! (okay, sorry, couldn’t help it. “Mooching” saves $$). Look for 2″ or 4″ size houseplants or any houseplant labeled “mini.”For your first terrarium a suggested planting would be a few low growing plants (irish moss), a medium-sized plant (rhizotomous begonia), and a tall plant (parlor palm). Irish moss is found at most garden centers, and begonias and parlor palms in most houseplant departments.

Gravel Choices

It’s important to ensure the plants you choose have the same light and moisture requirements. Just about any type of houseplant can be used in a terrarium. Most houseplants like to stay evenly  moist, but there are a few that prefer to be dryer. Read the label or look up the plant when in doubt. Common plants used in terrariums include mosses, ferns, fittonia (nerve plant), peperomias, carnivorous plants (like venus flytraps), pileas, ivy, and creeping fig.

Step 3: Gravel, Activated Charcoal and Potting Soil create the soil mix for the terrarium. Add about a 1″ layer of gravel, then cover over the top lightly with activated charcoal. This layer provides drainage and keeps the terrarium fresh. Activated charcoal is a natural filter and bactericide. On top of this layer, add a sterilized potting mix. Some gardeners use sheet moss or a small piece of landscape fabric in between the soil and gravel, but that’s up to you. This keeps the soil from falling in between the rocks for terrariums where you want a layered look.

Activated Charcoal

The soil mix for the terrarium should take up about 1/3 of the terrarium. To plant, you may want to pull off some of the root ball of the plant, and also gently tease any roots that are root bound. Set the largest plant inside the terrarium first, then add the other plants. They may not be stable until you’ve added more soil around the roots of the plants. Firmly press all the plants into the soil. Water gently, and then add accessories!

Ivy plants, a small Sinningia (front left) and Pink Polka Dot Plant in Mini Terra Cotta Pot

Step 4: Water the plants gently. It’s not necessary to wet all of the soil, just the soil around the plant. Open terrariums may need watering more than once per month, water only when soil is dry. Enclosed terrariums may need watering about once every 6 months. It’s best not to open the lid too frequently because this disturbs the mini ecosystem inside.

Caring for your terrarium is easy, simply remove dead or decaying leaves as they appear. Otherwise they can cause bacterial growth which may rot your plants. Clean the inside of the container with a non-toxic glass spray when needed. Replace any plants that have gotten to big, and pinch any plants that have gotten too leggy. Most terrarium containers last about a year before plants need replacing. For enclosed terrariums, it’s normal to have some condensation on the inside of the glass. However, if water is dripping on the inside, you’ve added too much. Take the lid off for a few hours each day until this stops.

Happy Planting, and please send me a message and/or photo of your terrarium project!

~Anne