Terrariums operate as self-sustaining greenhouses and are popular among busy plant lovers who may not have the time to sustain a full garden. Most terrariums only need water and care a few times a year, and serve as a beautiful and unique alternative to traditional plants and flowers that typically need more attention.
Terrariums are made up of stone, soil, charcoal, plants, and a little personality. You can make your own in under an hour with very few inexpensive materials. Here are some pointers for creating and caring for your own terrarium -- brought to you by our expert PHS horticulturists!
The fun thing about making a terrarium is you can choose almost any clear container or glass jar with a wide enough opening to allow you to add your selected plants. You can be as creative and resourceful as you want — upcycling something you have around the house or visiting your local thrift store are great ways to find something unique and help the environment. Popular options for terrarium containers include aquariums, goldfish bowls, mason or pickle jars, and Wardian cases.
Tip: Closed containers hold humidity, so they are ideal for tropical plants and others that need moist conditions. Choose open containers for cacti and other plants that need drier conditions.
Visit your local garden center or nursery to find plants that suit the size and shape of your container. You can choose from a wide variety of plants, including small potted versions of houseplants such as croton, pothos, lucky bamboo, and creeping fig. You want to choose terrarium plants with various foliage forms.
Terrarium containers do not have drainage holes, so it is important to create drainage layers to prevent plant roots from rotting. Start by putting a 2-inch layer of coarse gravel, sea glass, or beach stones on the bottom of your container.
Next, use a large spoon to add a quarter- to a half-inch layer of activated charcoal on top of the gravel to prevent fungi from growing on the stones when they are wet.
Spread a layer of sheet moss over the stones and charcoal to keep your next layer of potting soil from mixing in with the charcoal and stones.
Then, cover the gravel and charcoal with about 1 inch of sterile potting mix. In total, the base layer should take up one-quarter to one-third of the container to leave room for the plants to grow.
First, remove the plants you’ve chosen from their nursery pots and tease the roots apart if necessary.
Before planting, take time to design the plants’ arrangement for your terrarium. Set larger plants in the center, with smaller plants around it.
Now it’s time to put your plants into the soil. Use your fingers or a large spoon to dig a hole in the potting mix for each plant. Then, carefully place the plants in the holes and gently pat the soil down around them. There should be about a half-inch layer of soil on top to cover plants.
Tip: To create a pleasing, asymmetrical design, set the tallest plant toward the back or off-center and space the other plants around it.
This is the fun part! You can finish off your terrarium with a layer of bark chips or colored gravel for additional flair. Add small figurines, seashells, stones, or other appropriately sized whimsical items to truly personalize your mini garden.
Place your terrarium in bright but indirect sunlight. If you don’t have an area with bright indirect light, place a 100-watt light or fluorescent bulb over the garden for 16 to 18 hours each day.
The most common mistake is to overwater terrariums. For open terrariums, add water with a spray bottle or tablespoon once a week or when the soil is dry. Stop when you see the water begin to collect at the bottom of the terrarium.
For closed terrariums, you may only need to water every 4-6 months. Keep an eye out for condensation on the plants and dry soil. Condensation should form on the inside of the container and eventually run back down into the soil to serve as a water supply. If it forms on the plants instead, then the interior is too moist. Keep the cover off for a time each day until the plants are dry -- this can take 15 minutes to an hour. If the soil dries out, add water in small portions and stop if you see it begin to sit and not absorb into the soil.
Remove yellowing or damaged leaves and dead plants right away. Don’t fertilize your terrarium plants because it can stimulate excessive growth and lead to a build-up of salts in the soil.
Periodically clean the glass or plastic of your terrarium container both inside and out. If the glass gets too dirty or foggy, less light will reach your plants. Use a damp piece of newspaper or a lint-free cloth to wipe clean. Do not use harsh cleaning products.