Terrariums: Step by Step
Terrariums: The terrarium, or garden under glass, is a self-contained environment that produces its own climate.
Select a container*
There are four important requirements to consider when creating a terrarium:
- 1. The container must be glass or another clear substance through which light can pass.
- 2. There must be a large enough opening to allow for the emplacement of soil and plants.
- 3. The plants selected for a terrarium must have similar environmental needs.
- 4. The terrarium must be thoroughly cleaned before use (to prevent bacteria from growing)
Terrariums fall into two general categories:
- 1. Open: can tolerate some direct sunlight. However, too much sun may burn leaves that are in direct container with the sides of the container.
- 2. Closed: A closed terrarium can also be an open terrarium to which a cover has been added. Closed terrariums should be placed where they will receive bright light, but no direct sunlight. If placed in direct sunlight, the temperature inside the container rises considerably and literally cooks the plants.
*Before choosing a container, you must decide what you wish to grow in your terrarium. All plants in a terrarium should have similar light, moisture and other environmental needs. If you want to grow sun-loving plants in natural light, use an open terrarium. If you want to grow plants that require high humidity, the container should be closed.
Step 1: Drainage: A terrarium does not have drainage holes. Therefore, you must supply a drainage layer to prevent damage to plant roots. Crushed river gravel works well, but any small stone or bits of broken pottery will work. You want to use 1 to 4 inches of drainage material depending on the height of the container. Generally the depth of the drainage material, charcoal, and soil should equal about one-third the height of the container.
Step 2: Charcoal: On top of the drainage layer, place a thin layer of charcoal. This will help keep the soil fresh.
Step 3: Soil: The kind of soil used will depend on the type of plants you wish to grow (Cacti/succulent soil vs. potting soil). Use enough soil so that you can create a “hole” where you want to place the root ball of the plants. For example, if you are adding a fern to the terrarium that has a 4” root ball, you will need to add at least 4” of soil to the terrarium.
Step 4: Landscaping and Planting: Remember, plants grow. It is advisable to choose slow-growing plants and not to overplant. Make sure any necessary pruning is done prior to placing the plants in the terrarium and make sure plants are free of insects and disease. Place the largest plants in the terrarium first. Then add the smaller plants. Groundcover should be added last. Remember, you are making a miniature landscape, don’t forget to have fun with it and add in small animal figurines.
Heat: Closed glass containers trap and hold heat, and excessive heat is perhaps the main cause of death in terrariums. It is important that terrariums not be placed above radiators or in direct sunlight.
Lights: A newly planted terrarium should be placed in shade for about a week. Then adjust light according to the requirements of the plants. Most terrariums do better in diffused or filtered light than direct sunlight. Artificial light can also be used.
Too much sun: Leaves wilt and develop burned spots. Move the terrarium to a shadier spot.
Too little light: Plants develop tall, thin stems that are weak and unable to hold up leaves. Leaves are pale and fragile. Increase amount of light slowly.
Open terrarium: Test soil before watering. For plants that like moist soil, the top earth should feel barely moist before you add water. For cacti and succulents, touch below the surface layer. Lower soil should be only slightly damp.
Closed terrarium: These should rarely if ever need water.
Too dry: Leaves wilt and look pale. Moss becomes brown or faded. Add a little water and mist leaves.
Too much water: Excessive water encourages the growth of molds and causes plant decay. If terrarium walls have more than 25% condensation, remove the cover until walls clear. You may have to do this more than once. In a closed terrarium, there should be only occasional clouding.
Plant Growth: Terrarium plants should be scaled to the size of the container. As plants grow, prune back those that show signs of overcrowding. Clip and remove dead leaves. Replace dead plants. Remove plants that become too big.
Molds and Mildew: The presence of mold or mildew indicates that one of three things is wrong. The terrarium may contain too much water. Air circulation may be poor. Or you may be using plants that do not do well in closed terrariums. Remove infected plants immediately and correct the environment by letting the terrarium dry out or increasing air circulation.
Insects and Pests: Cut out infected area and spray with insecticide.
Cleanliness: Keep the container clean. Remove moisture or dust from the glass. Remove algae, which may form a green coating on the glass. Clean leaves and remove dead leaves and blossoms promptly to prevent the growth of fungi.
Recommended Plants for Low-light terrariums:
Ferns, mosses, baby’s tears, hypoestes, fittonia, ivy, peperomia, sanseveria, schefflera
Recommended Plants for High-light terrariums (Should be planted in open containers because desert plants require dry soil and low humidity. They also need warm temperatures and long periods of bright light):
Cacti, succulents, including jade, aloe, borro’s tail, earth stars, echeveria, haworthia, sedum