These are the top 5 terrarium care mistakes you need to avoid, according to houseplant experts

Our expert tips on terrarium care show just how easy it is to keep your terrarium looking good as long as you avoid these common pitfalls

geometric terrarium with plants
(Image credit: Prostock Studio/Getty Images)

With our easy terrarium care guide you will be able to keep your mini glass garden thriving for years to come. Although terrariums are a low-maintenance option and require less attention than many houseplants, they do require some TLC every now and then to keep them healthy. Plus there are some key mistakes to avoid if you want them to remain looking their best. 

Terrariums will often look after themselves once planted. Especially if you choose a closed design, which will create its own self-watering mini ecosystem. So you can't beat them if you're looking for as easy option. Just avoid the common pitfall of planting succulents in a closed design as conditions will be too humid for them and they won't thrive.

Where you keep your terrarium is also key to your success. Look into the light requirements of each of the terrarium plants you have in mind before choosing your winning combination and you will be on your way to hitting a successful formula.

set of large planted glass terrariums

Caring for terrariums is relatively easy as long as you follow some basic rules when it comes to watering, pruning and positioning them in the right spot 

(Image credit: Jacek Nowak/Alamy Stock Photo)

Are terrariums easy to care for?

Terrariums are easy to care for but there are one or two key considerations to take into account if you want to make sure yours is a long lasting and healthy centerpiece of your indoor garden

'It's important to regularly monitor and care for the plants in a terrarium, including watering, pruning, and providing adequate light and ventilation,' says James Kinsella from horticulture and botanical research experts Outplanted.com (opens in new tab). 'Overall, plants grow well in a terrarium as long as you give them the right conditions.' 

row of terrariums on windowsill and woman misting plant

The key to success is monitoring your terrarium regularly

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The 5 most common terrarium care mistakes (and how to avoid them)

You've invested time, effort and money into the indoor plants in your terrarium and want it to stay looking good for the longhaul. So follow our expert tips on what not to do if you want your terrarium to continue thriving.

1. Putting the terrarium in the wrong place

Keeping the terrarium in the right spot is important so be sure yours will fit in the position you have in mind when planning how to make a terrarium. Closed terrariums prefer bright, indirect light, while open ones like a well-lit spot that's not in direct sunlight. Again check out the requirements of the plants you have in mind. 

'Plants in airtight or closed terrariums recycle air,' explains Matt Kostelnick, senior horticulturist at Ambius (opens in new tab). 'During the day, sunlight promotes the growth of sugars during the process of photosynthesis, which converts carbon dioxide into oxygen, releasing it into the terrarium.' You may want to remove the lid of a closed terrarium every now and then to let in some fresh air as part of your terrarium care routine.

woman in blue dress holding planted jar terrarium

Choosing the right position is everything when it comes to terrarium care

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2. Watering your terrarium incorrectly

When it comes to watering plants in terrariums it depends on how many plants you have included in your scheme and what type they are, as well as whether or not your terrarium is an open or closed design. Remember also that terrariums retain water for longer than most other houseplants.

Terrariums don't need watering as much as many other indoor plants. 'The types of plants found in terrariums tend to be hardy plants that don’t require frequent watering,' says Matt Kostelnick. 'Also, the greenhouse-like structure of terrariums recycles water instead of evaporating.'

If your terrarium is closed it requires little or no watering, as it maintains the right level of humidity so becomes self-watering. You should be able to see condensation up to a third of the height of the terrarium. If there's very little condensation, try adding a tablespoon of water.

If the soil is completely dry and the leaves are wilting this is a sign that the terrarium needs watering. On average, if you have a closed terrarium you might need to water it once a month but if in doubt always water less. 

'Open terrariums benefit from being watered every 3-6 weeks,' says Matt. 'Rather than watering on a schedule, check the soil to see if and how much water your plants actually need.'

If you have a plant-heavy terrarium it will need to be watered more regularly. Make sure it's not in direct sunlight too, as this can lead to the soil drying out. Use a terrarium water bottle like this one from Amazon (opens in new tab) with a bendable nozzle to help get the water directed to exactly where it's needed.

woman watering terrarium with bottle

A water bottle with a nozzle like this one lets you direct the water flow exactly where you want it and reduces the chances of overwatering too

(Image credit: Kuziki/Getty Images)

3. Failing to trim terrarium plants

Pruning terrarium plants can be tricky due to the enclosed nature of the space and density of planting. You will need to trim back any plants that touch the sides of the terrarium or have grown so tall they are reaching the top. It's worth investing in a special set of extra long aquarium tools (available from Amazon) (opens in new tab) including scissors and tweezers that are perfect for the job. 

Use your new tools to keep leggy plants under control if you see them crowding the sides or top of the terrarium. Cut straggly stems down to a healthy leaf joint to encourage fuller growth.

Regularly trim any yellowing or dried leaves to keep the plants in your terrarium looking good. If you added a decorative layer of moss and it's looking a little jaded add a tablespoon of water every now and then to green it up.

If one of your plants is in trouble, there's no point holding on to it in the hope it will rally. If it's diseased this could spread to others in your indoor planter, plus of course it will detract from the aesthetics of your terrarium. When removing an ailing plant, be careful not disturb the roots of other plants. If you replace it with a new plant, it will need to be similar in size to slot neatly into your planting design.

tweezers being used to prune terrarium plants

Stock up on long-handled scissors and tweezers to make pruning and plant maintenance easier

(Image credit: Blue Jean Images/Alamy Stock Photo)

4. Letting the terrarium glass get dirty

If the glass is too dirty or foggy, it will prevent light from reaching your plants which can be detrimental to their health. 

Regularly dusting the outside is an important part of terrarium care as this allows light in, as well as showing off your plants. Either moisten a paper towel or use a soft clean cloth to simply wipe the glass. Avoid using glass cleaners as these may container chemicals that will be detrimental to your plants.

When cleaning the inside of the terrarium use distilled water or better still collected rainwater with a soft lint-free cloth. You only need the tiniest amount of water. Do not use a cleaning solution as that could contain chemicals that might be harmful to plants.

While you're there, don't forget to clean houseplants in your terrarium too.

woman lifting glass terrarium lid off with plants

Stay away from chemicals when cleaning your terrarium glass

(Image credit: Sergey Mironov/Getty Images)

5. Failing to act quickly if the terrarium gets bugs

If you have an open terrarium, monitor regularly for pests as part of your terrarium care. 'Gnats, mites, and mealybugs are all known plant parasites that can hitch a ride into terrariums via plants and substrate,' explains plant expert Dan Jones of Terrarium Tribe (opens in new tab).

If you think there's a problem take action immediately. Plants for terrariums aren't expensive and keeping a plant with an infestation in a terrarium means it could easily spread to other plants. 

'We recommend buying insecticidal soap [available from Amazon] (opens in new tab) and applying it to infected plants,' says Matt Kostelnick. 'You can also buy pebbles or rocks to deter gnats and avoid overwatering.' Check at your local gardening store for more advice.

If all else fails and the plant is still infested, the best terrarium care is to remove the entire plant. The same principal can be applied to your other indoor plant ideas too - don't let one ailing plant spoil your display.

terrarium being maintained with plants

Gently ease out any terrarium plants that are past their best or you suspect have a bug infestation and slot new ones into their place

(Image credit: Kuziki/Getty Images)
Sarah Wilson
Content Editor

Lifestyle journalist Sarah Wilson has been writing about gardens since 2015. She's written for Gardeningetc.com, Livingetc, Homes & Gardens, Easy Gardens and Modern Gardens magazines. Having studied introductory garden and landscape design, she is currently putting the skills learned to good use in her own space where the dream is establishing a cutting garden.