Common Terrarium Mistakes and How to Avoid Them


 The Spruce / Cori Sears

Terrariums, also known as gardens under glass, enable you to design and create tiny ecosystems of small plants and other decorative elements inside a glass enclosure. Terrariums bring contained, natural elements to your home or office and can last several years with proper care. Terrariums are generally low-maintenance and require less attention than most other house plants. However, they do require occasional maintenance and to maintain a healthy environment for your plants, you should avoid making the following mistakes.

illustration of common terrarium problems and mistakes
The Spruce /Catherine Song

Too Much Light

Most plants that are suitable for terrariums do not require extremely bright light. If placed in direct sun or extremely bright light, terrarium glass can act as a magnifier and burn the plants. Temperatures inside the terrarium can rise quickly and before you know it, the terrarium can become as steamy as a sauna. Most plants can't tolerate this kind of heat, so it's best to keep terrariums out of the direct sun.

Too Little Light

While too much light can cause problems, most plants need at least some light to survive. If your terrarium is not receiving enough indirect light, use grow lights or fluorescent lights to provide supplemental light or place the terrarium closer to a window that receives good, but indirect light.

Too Close to Heat Sources

The heat generated by a radiator or heating vent can kill your plants quickly. If you place your terrarium on or near a radiator or other heat source, most terrarium plants will not survive.

Overgrown Plants

Don't let terrarium plants become leggy and overgrown; you want to be able to admire individual plants and see the other decorative elements inside the terrarium. To keep your terrarium plants neat and tidy, trim them when they become overgrown and have crowded the terrarium, You can also prune their roots to keep them small.

Failure to Remove Dying Plants

If a terrarium plant looks like it might be diseased, is dying, or is not thriving, remove it immediately because its problems can infect other plants. Use a small shovel, terrarium tool, chopsticks, or long spoon to remove the plant, being careful not to disturb the roots of other plants. Replace the plant with one of a similar size and the same moisture and light requirements. Be sure to surround the roots with soil, leaving no air pockets.

Dirty Glass

Every once in a while, clean the glass of your terrarium both inside and out. If the glass is too dirty or foggy, it will be difficult for light to reach your plants. Use a damp piece of newsprint or a lint-free cloth. Do not use any harsh cleaning products on the inside of the terrarium because the chemicals in the cleaning products could harm your plants.

Over Watering

It is easy to over-water terrariums. One way to prevent over-watering is to use a spray bottle instead of a watering can. If you do over-water, absorb any extra water with a paper towel. Leave the top off of your terrarium until it has dried out.

Over Fertilizing

Most terrarium plants do not need to be fertilized. You want to keep terrarium plants small and inhibit their growth, so don't feed them because the plants will quickly outgrow their confined space.

Choosing the Wrong Plants

While it's possible to grow almost anything in a terrarium, it is important to choose plants that will thrive in the type of terrarium you are creating. If you're designing a closed terrarium, select plants that prefer a moist environment. Also, make sure to combine plants with the same light requirements. Low-light plants generally work best.

Planting Succulents in Closed Terrariums

Succulents generally thrive in high light and low moisture environments. If you plant succulents in a closed terrarium, the environment is far too humid for them to thrive. You can solve this dilemma by creating and planting them in an uncovered, open dish garden. Note that even a large jar will be too humid—airflow is important and air must be able to circulate around succulents.


Article Sources
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  1. Terrariums. Missouri University Extension