How to Make a Terrarium: A Stylish Miniature Glass Garden

April 11, 2016Anna Montgomery

Choose a terrarium size that will fit the area where you have bright, indirect light for 4 to 5 hours per day.
As long as it is clear (not tinted or cloudy) glass container, you can us
A container especially designed to hold a terrarium
An empty fish bowl or fish tank
A brandy snifter
An old glass jar, jug, or bottle with a wide enough opening at the top to allow access to the plants

Closed containers will retain the most humidity, followed by open terrarium, and dish gardens.
Open terrariums and dish gardens require more watering than closed containers but they do not suffer from the danger of too much high humidity over an extended period which can cause disease.
Closed terrarium do not require much watering but they need to be removed or cracked open once a week to allow moist air to escape.
Clean and disinfect the container before you start with dishwashing liquid or other mild cleaner. Make sure the container is dry before you start planting.

The container
Plants
Growing medium high in organic matter such as pre-packaged peat-lite mix (blend of peat moss, vermiculite, and perlite) is an excellent choice
Activated charcoal and pebbles
Gravel, sticks, rocks, seedpods, or bark for decorating
Spagnum moss (optional)
A small ceramic figure to suggest a natural setting (optional)
Wooden chopsticks for help arranging plants
A sharp knife
A kitchen baster to help with watering

Plants that have a low and dense growth habit work best. Choose only plants that are healthy and disease free.
Choose plants that fit the size of your container with plenty of room to grow. Choose plants of differing heights -- tall in the back, medium height in the middle, and short in the front -- but the plants should have similar light and watering needs.
Decide on a theme for the terrarium: woodland, tropical, desert
Choose plants that require the same amount of moisture and light (don't use tropical plants with plants native to the desert).
Use care with choosing succulents and cacti because moist conditions can cause plant rot, thus, choose an open container terrarium if you are using succulents.

Make sure your container is clean and dry.
Add the drainage material: pebbles, rocks, gravel, marble chips
Add activated charcoal (to eliminate chemicals that can harm the plants) in a 1/2-inch layer on top of the drainage material.
Spagnum moss added at this point will prevent the growing medium from sifting into the drainage area.
Add the growing medium which should be slightly moist, usually you will need at least 1-1/2 inches of medium to provide sufficient volume.
Choose a low, coarse textured plant for a focal point.
Before placing the plants, dig holes in the medium with a pointed stick or wooden chopsticks.
Remove the plants from their original pots and along with any extra soil to expose the roots. Place the plants in the growing medium and tamp down to firm it.
In a closed container, try not to touch the roots to the side of the container.
Mist the plants to remove excess growing medium. If the medium was moist enough, watering at this point should not be necessary.

Never overwater! Excess water can be almost impossible to remove.
A closed terrarium normally will not need water for 4 to 6 months.
A kitchen baster is a great way to limit the amount of water you add if watering is needed. Better a little too dry than too wet.
Water as needed by adding a couple of drops of water to each plant, near the roots.
Check every other week to ensure that there is enough water, but take care not to add to much water.
Over-watered plants will: droop, display black or rotten spots on their foliage, or develop rot on the leaves or roots
Under-watered plants will look: wrinkled, dehydrated
When watering a closed terrarium, do not replace the cover until the wet foliage has dried.

Although a terrarium is designed for growing plants with minimal care, it is a tiny growing garden. Some plants will thrive, and others may die. Occasionally it will become necessary to remove some plants and add others.
The terrarium will need additional air on a regular basis so try leaving the lid ajar for a couple of hours once a week.
The brightness and amount of sunlight and the number of plants will affect the way your terrarium uses water.
A few, small droplets of water should be allowed to condense on the glass of your terrarium.
If the droplets are numerous and/or large, the terrarium is retaining too much water. This can cause plants to wilt and rot more quickly.
If there is no condensation on your terrarium, there may be too much air reaching the interior space or too much light. This can also cause dry, dehydrated foliage. Try a different location for your terrarium or adjust the seal on the closure.

An open or closed terrarium should not receive direct sunlight which will cause heat buildup and injure the plants.
Most plants suitable for terrariums do not require extremely bright light to do well.
Plants receiving light from one direction will grow in that direction so to keep the terrarium attractive from the desired view, turn it occasionally to keep the plants growing normally.

Terrariums require little care, however, for the first few weeks check once a week to ensure that your plants are getting enough ventilation and not retaining too much moisture. After it is established, your terrarium checking every other week is sufficient.
Many plants in a terrarium will gradually outgrow their space. A little trimming brings into bounds. Pinching out tips before plants become too tall results in better growth than severe cutbacks.
Remove dead, damaged, or rotten foliage as quickly as possible, and replace overgrown or diseased plants are needed. Wooden chopsticks and a very sharp knife are handy terrarium tools.
Because plants in terrariums should not grow rapidly, terrariums seldom need fertilizer. Do not fertilize for at least a year after planting. If after the first year, the plants appear yellowish and seem to lack vigor, a light fertilization may be necessary. Use a water-soluble, houseplant fertilizer at about 1/4 the rate recommended for nomal houseplants. Do not allow any of the fertilizer to remain on the foliage.