A terrarium is a gardening container designed to allow heat and light to enter and confine moisture. Terrariums can be entirely open or enclosed; the type you select will determine the plants that will thrive best in your terrarium. Sometimes referred to as a "garden under glass," a terrarium makes a beautiful and impressive gift, even for people who don't consider themselves to have a green thumb.
You can make a basic terrarium with a few inexpensive materials in less than an hour.
Before Getting Started
Larger terrariums can handle houseplants that are somewhat large but avoid fast-growing species or those that develop large leaves that will block light needed by the smaller plants. When considering terrarium plants, look for plants that thrive in low to medium light. For visual appeal, choose a mix of leaf sizes, texture, and color.
Select plants that won't mind the naturally humid environment of a terrarium. Avoid cactus and succulents in an enclosed terrarium. Those plants work best in fully open containers filled with a potting mix containing plenty of coarse sand.
Here are a few examples of plants to include in a terrarium:
- African violet
- Polka dot plant
- Small ferns
- Lucky bamboo
- Nerve plant
- Prayer plant
- Club moss
- Creeping fig
What You'll Need
- Large spoon or garden trowel
- Small garden snips or scissors for trimming plant roots
- Spray bottle
- Glass container, we think ours are pretty awesome
- Clean aquarium gravel or small rocks
- Activated charcoal (found at a nursery or pet supply stores)
- Terrarium plants
- Sterile potting mix
- Sheet moss
- Decorative elements (optional)
Choose the Plants
Most garden centers stock miniature plants for terrariums, sometimes in the store section containing fairy garden accessories. Choose terrarium plants with various foliage forms and heights that are small enough to fit in your container, preferably without touching the sides of the terrarium.
Add Drainage Layers
A terrarium container does not have drainage holes, so you'll need to create a drainage layer to keep water away from plant roots. Start with about a 2-inch layer of gravel or crushed stone in the bottom of the terrarium. Next, use a trowel to add a 1/4-inch - 1/2-inch layer of activated charcoal on top of the rocks to help with drainage.
Add Moss and Potting Mix
Next, add a layer of sheet moss over the stones and charcoal to keep the next layer, the potting soil, from mixing in. The moss also adds visual interest to your terrarium.
With a trowel, add slightly damp, sterile potting soil on top of the moss. Do not use a potting soil mix with fertilizer already incorporated; terrarium plants don't need the extra fertilizer.
Add as much potting mix as you can—at least a couple of inches. Make sure to keep the soil level low enough so that the plants will fit inside the container with room to grow but without touching the top of a closed terrarium.
Prepare the Plants
Before planting, decide on the design of your terrarium. Choose the spots where you'll place tall and short plants and where you'll create mounds and dips in the soil to create interesting contours.
Remove the plants from their nursery pots. If a plant is rootbound, tease the roots or use a pair of small garden ships to trim off some longer roots. Removing a few roots, called root pruning, will hinder a plant's growth, which is essential when growing plants in the confines of a terrarium. Also, trim off any yellowed or damaged leaves.
Shake off any excess soil left on the plants. Use a long spoon or your fingers to dig a planting hole for each plant. Place each plant in its spot and gently pat the soil down to eliminate air pockets, and secure each plant firmly in the potting medium.
If you'd like, decorate the inside of the terrarium with small figurines, shells, decorative stones, or other whimsical accents spaced among the plants.