Do Terrariums Need a Lid? Exploring the Pros and Cons

Plants (Cacti and Succulents) Suitable for Open-System Terrariums

• Aeonium
• Aloe vera
• Burro’s tail
• Cactus
• Crown of thorns
• Devil’s backbone
• Echeveria
• Flaming Katy (Kalanchoe)
• Hens and chicks
• Jade plant
• Panda plant
• Pencil plant

Find a Display Site

Before purchasing plants and supplies, consider where the terrarium will be displayed. It’s a good idea for it to blend with the interior style. Decide how it will be shown, whether on a table or a plant stand.

It’s best to keep the terrarium in a dedicated space. Avoid moving it frequently, as changes in light intensity and duration may harm plant health. Find a location with bright, indirect light. Often, an eastern exposure with morning sun is ideal for terrariums. Similarly, a western exposure may work well if afternoon heat is avoided.

Don’t put a terrarium near a window because the sun’s rays can heat the container up and burn the plants inside.

Plant-supply departments often carry an array of terrarium supplies, which are also available online.

Beyond the container, decorative accessories can enhance the design theme. These items may be ceramic, glass, metal, or plastic—anything impervious to moisture. They can be big or small parts of the design, or they can be left out for a natural, uncluttered look.

This example uses heat-treated bark. Avoid using bark intended for outdoor landscapes, as it may harbor pathogens that could introduce disease into the terrarium. For indoor plants, heat-treated bark is a nice alternative to moss, or it can be mixed with moss to add pattern and texture. Similarly, it may be advisable to use only one variegated, fancy-leaved plant along with other green plants.

Horticultural-grade charcoal consists of pure carbon chips, about one-fourth of an inch long. This material provides a filtering effect for water that has percolated from the soil mix. You can also use aquarium charcoal, although it may be slightly more expensive. Only clean, washed gravel and sterile, soilless potting mix should be used.

When water droplets (condensation) form on the inside walls or lid of the terrarium, open the lid for about an hour to allow excess moisture to evaporate. Continue this process until you see very little, if any, condensation. At this point, the terrarium ecosystem has reached equilibrium and can withstand long periods without additional watering—from weeks to years!

One goal of terrarium culture is to encourage slow growth, which reduces the need for pruning. Air, moisture, and sunlight aid in photosynthesis, which converts light energy into carbohydrates. This is all a terrarium needs to thrive. There is no need to add fertilizer to a closed system.

A terrarium typically has a display life of no more than one or two years. As plants mature, they may outgrow the container, necessitating pruning or removal. This is a great opportunity to refresh the design by rearranging existing plants or adding new ones—a fun and relaxing activity for any time of year!

• Container (2-gallon glass jar)
• Choose plants like the Neanthe bella palm, the nerve plant, and the Boston fern ‘Fluffy Ruffles.’
• Finely chopped, heat-treated bark
• Gravel
• Horticultural-grade charcoal
• Potting mix
• Moss (undyed sheet moss)
• Decorative items (miniatures, shells)
• Mist bottle and water
• Scissors or snips
• Newspaper or other paper

*Not all materials are necessary for every project. Plant supply departments often carry a variety of terrarium supplies, which are also available online.

• Before building starts, water the plants in their original pots a few hours or the day before. Be sure to wash the terrarium container before using it. Put down some newspaper on your work surface to make it easy to clean up.
• Put one inch of gravel in the bottom of the cup.
• Pair up two or three sheets of newspaper or other paper to make a funnel. Slowly add about ¼ inch of charcoal through the paper funnel.
• Next, fill the pot with about 2 inches of soil mix. Make a hole in the ground big enough for the plant’s root balls to fit.
• Break up the soil at the top and bottom of the root ball as you take plants out of their pots.
• Often, more than one plant of the same type is in a pot. Carefully use your fingers to open the root ball and cut the plants into smaller pieces.
• If some leaves or stems touch the bowl’s sides or lid, you may need to cut them back.
• Put the tallest plants in the middle and the rest of the plants around it. Allow a bit of space between them. Evaluate the need for additional pruning.
• Cover the roots with soil and put the plants in place.
• Now, it’s time to water the terrarium. Mist the inside of the glass jar with a mist bottle. This not only keeps the soil moist, but it also helps get rid of charcoal dust or other organic matter on the glass. When the soil’s color looks saturated, you know it’s wet. Do not fully soak the soil, but make sure to mist the root ball area of each plant a lot. You can carefully add water to the terrarium at any time, but you can’t take it out.
• Break up big chunks of moss and spread them out on top of the soil. Add chopped bark to other patches. Finally, add decorative items.

To establish the moisture balance within the terrarium, follow these steps:

• When you’re done with the project, leave the container open for about 24 hours to let the extra water vapor escape.
• Replace the lid for 24 hours.
• Take off the lid for another 24 hours to let the condensation evaporate.
• Replace the lid again for another 24 hours.

Repeat this process until no moisture collects on the inside glass of the terrarium. At this point, the terrarium has reached equilibrium and will not need watering for weeks, or even months.

Foliage or stems resting against any interior glass surface can harm the health of the leaf, plant, and the entire terrarium system. The leaf surface gives off water vapor; if it is near the glass, moisture will be trapped, creating an environment conducive to disease. Similarly, it is best to keep plants from touching each other to prevent the rapid spread of disease.

Do Terrariums Need Air? The SIMPLE Answer!

FAQ

Can you have a terrarium without a lid?

A tropical terrarium with moss will greatly benefit from the increase in humidity with a closed lid. It’s still possible to have a tropical terrarium without a lid, but you’ll have to mist it constantly, and it’s going to be much more prone to dry out.

Should my terrarium have a lid?

It’s best to get a loose-fitting lid that allows some air to escape so that the plants can breathe. If you seal off your terrarium from the air, mold will be able to grow and kill your plants. Be sure that even with a loose fitting lid, once a week or so, you open the container to encourage air movement.

Do terrariums have to be covered?

Terrariums can be covered or uncovered. I prefer the covered version for the simple reason that it requires less maintenance. A covered terrarium is a self-sustaining system where the water vapor is trapped creating a high humidity environment.

Can a terrarium have an open top?

Open Terrariums: An open terrarium is one that lets air in. These terrariums are typically filled with plants that prefer a drier environment, such as succulents and cacti.