How To Make a Terrarium

Select the proper terrarium container

For a closed terrarium
Choose a container with a lid that will capture moisture and hold enough soil and drainage layers to support the growth of your plants.

For an open terrarium
Choose a container with an open top that can hold enough layers to support the growth of your plants. Keep in mind that you will want to reach in with your hand or small gardening tools. Therefore, it will be easier to plant and maintain a vessel with a wider mouth than a narrow neck. It is doable but much more challenging to plant, maintain, and troubleshoot a vessel with a small opening.

Select plants for the terrarium

For a closed terrarium
Choose plants that will thrive in a high-moisture environment. Speak with someone at your plant nursery to select plants that do well in a closed terrarium. To add visual interest to your terrarium, select plants that are visually different in height, leaf shape and color.

For an open terrarium
Choose plants that will thrive in an arid environment. Think of cacti, succulents or plants that will remain hardy in drier soil. Consult your local plant nursery to identify plants that will thrive in an open terrarium. Select plants with visually different heights, leaf shapes and colors for your terrarium to add visual interest.

Start with a draining base layer

Lay in a 1/2-inch of sand. On top of that, add one inch of small to medium pebbles or small stones as your base. These layers will pull the water away from the roots of the plants, helping to prevent decay and plant diseases. Do not be afraid to add a thicker layer of either.

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Lay in landscape fabric and add activated charcoal

To prevent the charcoal from seeping down and mixing into the stones and sand, cut your landscape fabric as close to the shape of your vessel as possible and lay it over the layer of pebbles then add charcoal over the landscape fabric. The charcoal will help filter toxins and help keep your plants healthy from disease. Most do not add charcoal to an open terrarium as it is a dry environment and less likely to develop fungus, but it will not hurt to have a little more insurance for healthy plants.

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Add a layer of spagnum moss

If you’re building a closed terrarium, lay a 1/2-inch to 1-inch layer of sphagnum peat moss. This layer will absorb water and hold moisture around your roots, extending the time between watering sessions.

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Add terrarium soil

Add two to three inches of soil. This will be your thickest layer, where your plants will grow their roots. Feel free to create height and undulations with the dirt. This will allow you to easily create visual interest and height differences with your plants. If you are planning to add any decorative elements, this is the time to think about placement and take advantage of various levels to place them. You may use cactus dirt or mix regular potting soil with cactus dirt for this layer for open terrariums.

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Plant terrarium

Place and plant.  Feel free to move things around.  If you are creating height with the soil, this will be a great area to place plants that may need less moisture and the water will drain down and dry out faster.

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Add small pebbles/living moss

In open terrariums, you can add small pebbles around plant placement. In closed terrariums, you can do the same and add living moss. This will create texture and help prevent erosion by holding your layers in place when you water.

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Maintaining a terrarium

For a closed terrariums:

• Due to the high moisture level, a closed-lid terrarium is it a higher risk for root rot, fungus and disease. Make sure your not overwatering your plants and supply the terrarium with an adequate drainage layer.
• Take the lid off once a month for 20 – 30 minutes to create air circulation.
• Do not put it in direct sunlight. The glass serves as a magnifier, which may burn your leaves.
• Plants that thrive in a moist environment tend to grow faster. Plan to give them space to grow.
• Water every two weeks.  You may also mist it with a thin sprayer once a week.  You want moisture in the vessel, but you do not want the roots in your plants to decay. Plan to be vigilant and observe the environment.  Add water as you see fit.

For an open terrarium

• If your open terrarium contains succulents, you may place it in direct sunlight.
• Leave room for your plants to grow. Plants that thrive in a dry environment will grow slower than in a wet environment, but they still need space to grow.
• Water once a week or when the dirt looks dry.

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FAQs

Q: How long should a terrarium last for?

A: A terrarium will last as long as someone is dedicated to properly caring for its plants and environment. Terrariums are living projects that require constant adjustments to light, temperature and watering schedule. They have been known to last for decades. On average, terrariums last four months to two years. Most people give up far too easily on their terrariums because they aren’t aware of how much attention they may require.

Q: Is it OK to have insects in my terrarium?

A: Regardless of whether you see them or not, the probability of your terrarium having insects is high, and they most likely arrived with the soil. Therefore, …yes, insects can serve a role inside your terrarium’s environment and help keep it stable. If you see an occasional insect among the leaves, try to identify it before determining if you want to get rid of it or not. Damaged leaves are a good sign that an insect is not beneficial to your terrarium.

Q: How often should  I water my terrarium?

A: The amount of water or moisture your terrarium requires to maintain an optimal environment will depend greatly on the size of your terrarium, the plant selection and whether it is a closed or open terrarium. Generally speaking, a closed terrarium wants constant moisture, and an open terrarium wants to be dry, dry and then wet enough to keep the plants alive.  You must observe your plants as they settle into their new environment.  Plants give off signs if they are happy or need more attention – you just have to watch them closely. Too much water or not enough water will damage your plants.  Find the happy medium, and you will have a successful terrarium.