What to Grow in a Glass Terrarium? | Plants That Thrive

Small, slow-growing, humidity-tolerant plants like mosses, ferns, and fittonia are the best choices for a glass terrarium.

The right plants for a glass terrarium come down to one question: is your container sealed or open? That single detail determines which species will thrive and which will rot within weeks. For closed glass vessels, you want compact tropicals that love humidity and indirect light. For open containers, you can shift to plants that tolerate drier air and more airflow. Getting this match right is the difference between a self-sustaining mini-garden and a soggy, moldy mess.

Most glass terrariums follow the same recipe: a drainage layer of gravel, a thin charcoal layer, and a soil mix that holds moisture without staying soggy. Purdue University Extension recommends 1 part sand, 1 part peat moss, and 1 part loam, with 1 to 3 inches of gravel or other drainage material at the bottom. Once that base is set, plant selection becomes the make-or-break decision.

Best Plants for Closed Glass Terrariums

Closed terrariums trap humidity and create a mini greenhouse effect, so they suit plants that naturally grow on humid forest floors. These species stay compact, tolerate low airflow, and flourish in bright, indirect light.

• Mosses — the backbone of any closed terrarium; they carpet the soil and thrive in constant moisture.
• Small ferns like maidenhair and button ferns — they love humidity and stay petite with regular trimming.
• Fittonia (nerve plant) — a low grower with dramatic veined leaves that signals thirst by wilting dramatically.
• Pilea varieties like the friendship plant — compact, forgiving, and quick to fill space without outgrowing it.
• Peperomia — thick leaves hold water well, and most varieties stay small for years.
• Baby tears (Soleirolia soleirolii) — a dense, trailing ground cover that forms a lush green carpet.
• Selaginella (spikemoss) — a fern-like trailing plant that loves consistently moist soil.
• Polka dot plant (Hypoestes) — adds color with pink or white speckled leaves and responds well to pinching back.

All of these share the same needs: high humidity, indirect light, and minimal airflow. Iowa State University Extension recommends medium to bright, indirect sunlight for closed terrariums. Keep the vessel out of direct sun, since glass amplifies heat quickly and can cook the plants inside.

What Grows in an Open Terrarium

Open containers lose moisture fast and give plants constant airflow, so they suit a different plant family entirely. Succulents and air plants (Tillandsia) are the standard choices here because they tolerate dry conditions and need their roots to breathe.

Popular succulent picks include haworthia, echeveria, and jade plants — all small, slow-growing, and forgiving of occasional neglect. Air plants don’t need soil at all; they absorb moisture through their leaves and can be nestled on top of the drainage layer or mounted on driftwood. One caution: these plants cannot share a home with the moisture-loving tropicals above. Mixing succulents with ferns creates incompatible care needs, since one group wants dry roots and the other wants constant humidity.

How to Water and Care for Terrarium Plants

Watering is where most terrariums fail. Closed systems need remarkably little water; Iowa State notes many closed terrariums need water only every 3 to 6 months, depending on plant load, container size, and conditions. The sealed environment recycles moisture continuously. If you see persistent condensation on the glass, uncover the vessel to let excess moisture escape.

Keep the temperature between 65 and 70°F (18–21°C) and away from cold drafts. Prune plants regularly so leaves never touch the glass — contact points trap moisture and invite rot. Skip fertilizer almost entirely; terrariums need little or none, and feeding speeds up crowding. If you’re starting fresh, a well-made vessel matters as much as the plants, and our roundup of large glass terrarium options covers tested containers that give roots room to grow.

Which Plants to Avoid in Glass Terrariums

Skip fast-growing species, deep-rooted plants, and anything that needs strong sun or frequent drying. Large, vigorous growers quickly crowd the space and force constant pruning. Plants that need dry roots, like most cacti and drought-tolerant succulents, will rot in a sealed glass environment where humidity stays high.

Overwatering is the single most common failure. Persistent condensation, soggy soil, and standing water at the bottom all point to too much moisture. If water pools at the base, tip the vessel gently to drain it and let the soil dry before closing the lid again. Use a clean container and clean tools at setup to keep mold and contamination at bay.