What Type of Terrarium Should You Make?

Before buying plants or pouring pebbles into the nearest cookie jar, decide whether you want a closed or open terrarium. This choice controls nearly everything that follows, including plant selection, watering frequency, and placement.

Closed Terrarium

A closed terrarium has a lid, stopper, or cover that traps moisture. Water evaporates from the soil and leaves, condenses on the glass, and eventually returns to the growing medium. It functions as a miniature water cycle, although it is not completely maintenance-free.

Closed terrariums are best for small tropical plants that enjoy consistently moist soil and high humidity. Suitable choices include fittonia, miniature ferns, baby’s tears, small peperomias, pilea, mosses, and compact creeping plants. Cacti and most succulents are poor choices because the humid, enclosed environment encourages rot.

Open Terrarium

An open terrarium has no lid and behaves more like a decorative indoor container garden. Moisture escapes more easily, so it must be watered more often than a closed setup. The increased airflow also reduces persistent condensation and some fungal problems.

Open containers can hold plants that prefer drier conditions, including small succulents and haworthias. However, even drought-tolerant plants need excellent drainage, strong light, and restrained watering. A glass bowl filled with wet soil is not a desert simply because you added a plastic camel.

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Supplies for a Basic Terrarium

You do not need an expensive kit. Most basic terrarium supplies are available at garden centers, craft stores, or around the home.

• A clean, clear glass or plastic container
• Fresh indoor potting mix appropriate for the plants
• Two to four small, healthy plants
• Optional gravel or decorative stones
• Optional horticultural charcoal
• Sheet moss or decorative moss, if desired
• A spoon, narrow scoop, or small trowel
• Long tweezers or chopsticks for narrow containers
• A spray bottle or small watering container
• Decorative stones, bark, or miniature ornaments

Choose a colorless container because tinted or cloudy glass reduces the amount of light reaching the plants. A wide opening is easiest for beginners. Bottles with narrow necks look impressive, but planting through them can feel like performing surgery with salad utensils.

Wash the container thoroughly and allow it to dry. Inspect plants for pests, damaged leaves, mold, and unhealthy roots before bringing them into the terrarium. Starting with clean materials and healthy plants is much easier than treating an insect problem inside a miniature rainforest.

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How to Choose the Best Terrarium Plants

The best terrarium plants stay relatively small, tolerate indoor light, and share similar moisture requirements. Mature size matters more than the plant’s size at the store. A tiny plant that naturally grows several feet tall may soon press against the glass like it is trying to escape.

Good Plants for Closed Terrariums

• Fittonia: Colorful veins, low growth, and a preference for humidity make it a classic choice.
• Miniature ferns: Button ferns, heart ferns, and other compact types enjoy humid conditions.
• Small peperomias: Many have attractive foliage and manageable growth habits.
• Pilea: Compact varieties provide fine texture and fresh green color.
• Earth star bromeliads: These add dramatic color and a low, spreading shape.
• Moss: Moss can soften bare soil and create a woodland appearance.

Good Plants for Open Terrariums

• Haworthia
• Small echeveria varieties
• Miniature aloe varieties
• Compact sedums
• Other slow-growing succulents with similar needs

Do not mix tropical plants with desert plants. A fern and a cactus may look charming together for a photograph, but one wants humid soil while the other wants to dry out. Select plants that agree on light, temperature, moisture, and soil conditions.

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Understanding Terrarium Layers

Many terrarium diagrams show several perfectly separated layers. These layers can be useful, but they are not a substitute for careful watering.

Optional Drainage or Reservoir Layer

A shallow layer of gravel can create a place where a small amount of excess water collects below the soil. It also provides visual contrast. However, rocks at the bottom do not make water magically travel away from the root zone as it would through a drainage hole. Too much water can still saturate the soil and rot the roots.

Optional Horticultural Charcoal

A thin layer of horticultural charcoal is often added above the stones. It may help keep the enclosed environment fresher, but it cannot rescue a terrarium that is chronically overwatered. Use horticultural charcoal rather than barbecue briquettes, which may contain additives.

Potting Medium

Use a fresh, lightweight indoor potting mix rather than soil dug from the yard. Garden soil can compact inside a container and may introduce insects, weed seeds, or disease organisms. Add enough potting medium to accommodate the roots of your largest plant. In many containers, a soil depth of approximately 2 to 4 inches is sufficient.

For tropical terrariums, a quality houseplant mix containing ingredients such as peat or coconut coir, perlite, and fine bark usually works well. For an open succulent terrarium, choose a gritty cactus or succulent mix that dries more rapidly.

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How to Make a Basic Terrarium Step by Step

Step 1: Clean and Plan the Container

Wash the container with warm, soapy water, rinse it thoroughly, and let it dry. Set the empty container where you plan to display it. Consider which side will face the viewer and whether the arrangement will be viewed mainly from the front or from every direction.

Step 2: Add the Foundation

If you are using gravel, add a shallow layer to the bottom. A depth of roughly one-half to one inch is enough for most beginner containers. Add a light sprinkling of horticultural charcoal if desired. Avoid creating excessively deep decorative layers that leave too little room for soil and roots.

Step 3: Add the Potting Mix

Spoon in the potting medium without packing it tightly. Create gentle slopes or raised areas if you want the landscape to appear more natural. Make the soil deep enough to cover the root systems without burying plant stems.

Step 4: Test the Arrangement

Before removing plants from their nursery pots, place the pots beside the container and experiment with different arrangements. Put the tallest plant toward the back in a front-facing terrarium or near the center in a container viewed from all sides.

Combine contrasting leaf shapes and colors while leaving room for growth. A successful design often includes a focal plant, a medium-height companion, and a low ground-covering plant. Resist the urge to fill every inch. Empty space gives the composition depth and prevents immediate overcrowding.

Step 5: Prepare the Plants

Gently remove each plant from its nursery pot. Loosen tightly circling roots and shake off some excess potting medium if the root ball is too large. Trim dead foliage and remove any damaged roots with clean scissors.

Step 6: Plant the Terrarium

Make a hole in the soil, lower the roots into it, and gently firm the potting mix around the plant. Continue with the remaining plants, working from the back toward the front. Use chopsticks, long tweezers, or the handle of a spoon when working through a narrow opening.

Step 7: Add the Finishing Details

Cover small bare areas with moss, fine gravel, bark, or decorative stones. Add one or two miniature accents if desired, but keep them proportional. The goal is a tiny garden, not a crowded yard sale inside a jar.

Step 8: Water Conservatively

Add a small amount of water around the plants. A spoon, pipette, or narrow-spout bottle gives more control than pouring from a large watering can. The soil should become evenly moist, not muddy. Water running visibly into the bottom reservoir is a warning to stop.

Step 9: Clean the Glass

Brush soil from the leaves and wipe the inside of the glass with a clean cloth attached to a spoon or chopstick. Clean glass improves the appearance of the finished terrarium and makes future condensation easier to evaluate.

Step 10: Allow the Terrarium to Adjust

For a closed terrarium, leave the lid off for a day if the soil is very moist. Then close it and observe the glass over the next week. The system may need minor adjustments before it reaches a stable moisture balance.

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Where to Place Your Terrarium

Place most tropical terrariums in bright, indirect light. An east-facing window or a position several feet from a brighter window often works well. Avoid intense direct sunlight, especially during the afternoon. Glass traps heat, so a closed terrarium in strong sun can overheat quickly.

Rotate the container occasionally if the plants lean toward the light. If new growth becomes pale, stretched, or unusually thin, the terrarium may need a brighter location. If leaves bleach, develop scorched patches, or wilt while the soil remains moist, the light or heat may be excessive.

Keep the terrarium away from heating vents, radiators, fireplaces, and strong air-conditioning drafts. Although the plants are protected by the container, sharp temperature changes can still cause stress.

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How to Water and Maintain a Terrarium

Watch the Glass Before Adding Water

A closed terrarium should not have heavy condensation covering the glass all day. A light mist in the morning or evening can be normal. Constant droplets, dripping glass, or swampy soil indicate too much moisture. Remove the lid for several hours or a full day to allow excess water to escape.

If there is no condensation for several days and the soil looks dry, add a few spoonfuls of water. Closed terrariums may go weeks or longer without watering once balanced. Open terrariums require more frequent checks because moisture evaporates into the room.

Prune Before Plants Become Crowded

Pinch or trim plants when they begin touching the glass or crowding their neighbors. Remove yellow leaves and fallen plant material promptly. Decaying foliage in a humid enclosure can encourage mold.

Use Fertilizer Sparingly

Most basic terrariums need little or no fertilizer during their first year. Rich feeding encourages rapid growth, and rapid growth is not especially helpful in a container where every inch matters. If mature plants become pale despite receiving suitable light, use a heavily diluted houseplant fertilizer only during active growth.

Inspect for Pests

Check leaf undersides and stems for fungus gnats, mites, mealybugs, or scale. Isolate the terrarium from other plants if you discover pests. Removing a badly infested plant is often safer than repeatedly spraying chemicals inside a confined container.

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Common Terrarium Problems and Solutions

The Glass Is Always Foggy

Cause: Excess moisture or insufficient ventilation.

Solution: Open the lid until the glass clears. Remove standing water with a pipette or absorb it carefully with a rolled paper towel.

The Plants Are Turning Yellow

Cause: Overwatering, poor roots, excessive heat, or natural leaf aging.

Solution: Check the soil before adding water. Remove damaged leaves and inspect the roots if the plant continues declining.

White Mold Appears

Cause: Decaying leaves, saturated soil, or stagnant air.

Solution: Remove affected material, ventilate the container, and reduce moisture. Clean tools before using them elsewhere.

Plants Grow Tall and Floppy

Cause: Insufficient light or a naturally vigorous plant variety.

Solution: Move the terrarium to brighter indirect light and prune stretched growth. Replace plants that are simply too large for the container.

The Soil Smells Sour

Cause: Waterlogged growing medium and decomposing roots.

Solution: Vent the container immediately. If the odor remains, remove the plants, discard the saturated medium, clean the container, trim unhealthy roots, and rebuild with fresh mix.

Beginner Experiences: Lessons From Realistic Terrarium Builds

The first terrarium many beginners make is usually attractive for about three days. Then the glass fogs over, one leaf touches the side, and the owner begins wondering whether the jar has developed its own weather service. This is normal. Terrarium building is less about following a perfect recipe and more about observing how plants respond inside a confined environment.

Experience One: The Overwatered Woodland Jar

A typical beginner selects fittonia, a small fern, and moss for a lidded jar. The planting goes smoothly, but the builder waters the container as thoroughly as an ordinary flowerpot. By the following morning, large drops cover the glass. Water has collected beneath the soil, and the moss looks as if it has booked a beachfront vacation.

The best response is not to add more materials or immediately rebuild everything. Removing the lid for a day often allows enough moisture to escape. Once the condensation becomes lighter, the lid can be replaced. This experience teaches the most important terrarium rule: it is easier to add water than to remove it.

Experience Two: The Beautiful but Incompatible Plant Mix

Another common build combines a cactus, a fern, and fittonia because the textures look interesting together. Visually, the arrangement is excellent. Horticulturally, it is a disagreement waiting to happen. The fern and fittonia want consistent moisture and humidity, while the cactus needs stronger light, greater airflow, and dry periods.

Within several weeks, either the tropical plants wilt from dry conditions or the cactus softens from excess moisture. The lesson is simple: design begins with compatibility. Color and shape matter, but shared growing requirements matter more. A successful terrarium is a community, not a reality show.

Experience Three: The Fast-Growing Ground Cover

Baby’s tears can create a beautiful green carpet, but it may spread aggressively in favorable conditions. A tiny starter plant can eventually push into its neighbors and cover decorative stones. This is not necessarily a failure. It simply means the terrarium requires pruning.

Trimming the plant with clean scissors restores open space and improves airflow. Some of the cuttings may even be rooted in another small container. Beginners often worry that pruning will ruin the miniature landscape, but selective trimming usually makes the design look more intentional.

Experience Four: The Terrarium Placed in Direct Sun

A finished terrarium looks so cheerful on a sunny windowsill that the location seems perfect. Unfortunately, strong sunlight can heat the air inside the glass quickly. Leaves may wilt or develop pale, scorched areas even though the soil is moist.

Moving the container to bright, filtered light usually prevents further injury. A thin curtain, nearby shelf, or east-facing exposure can provide enough light without turning the terrarium into a botanical oven. This experience demonstrates why plant care depends on both light intensity and temperature.

Experience Five: The Terrarium That Finds Its Balance

The most satisfying stage arrives after several weeks. New leaves appear, the soil remains lightly moist, and only a small amount of temporary condensation forms. The plants begin growing into the arrangement rather than merely sitting in freshly disturbed soil.

At this point, the best maintenance strategy is restraint. Check the terrarium regularly, remove dead leaves, and resist watering simply because caring for plants feels productive. A balanced closed terrarium may need surprisingly little attention. Its quiet stability is part of the appeal: a tiny green world continues growing while you handle the considerably less organized ecosystem outside the jar.

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Final Thoughts

Learning how to make a basic terrarium is mostly an exercise in matching the right plants with the right environment. Choose a clear container, use fresh potting medium, group plants with compatible needs, water cautiously, and provide bright indirect light. Those five decisions prevent most beginner problems.

Do not worry if your first design needs adjustment. Plants grow, moisture levels change, and even carefully arranged moss occasionally develops ambitions. Observe the terrarium rather than following a rigid watering schedule. With modest pruning and patient moisture control, your miniature garden can remain attractive for months or even years.

Note: This article synthesizes practical guidance from U.S. university extension programs and botanical institutions, including the University of Missouri, Penn State, the University of Minnesota, Clemson University, the University of Illinois, Oklahoma State University, the University of New Hampshire, North Carolina State University, the University of Maryland, Brooklyn Botanic Garden, and the New York Botanical Garden.