Terrariums are a fun way to let your imagination run wild while you garden. “You can create a mini-ecosystem in a terrarium,” says Marc Hachadourian, director of glass house horticulture and senior curator of orchids at New York Botanical Garden. “Terrariums also allow you to grow plants, such as some ferns, that typically don’t do well without humid conditions.”
A terrarium is like a tiny greenhouse: The plants release water vapor, which condenses, keeping moisture inside the tiny structure. “This keeps the interior environment stable and moist,” says Hachadourian.
One more benefit? Terrariums are the perfect way to keep curious cats and dogs away from your plants if they typically like to nibble on your houseplants! (These are the best pet-friendly houseplants you don't need to keep behind glass.)
How to Make a Terrarium
You can make a terrarium out of almost any container, including pretty miniature greenhouses, old fish tanks, or decorative bottles. You can use either open containers, with no lid, or closed containers.
Your first layer in the bottom of the container should be gravel so the plants aren’t sitting directly in water. Then add a few inches of any type of potting mix on top. Only about a quarter to one-third of the container should be filled with gravel and soil for the most attractive presentation, says Hachadourian.
You even can add tiny decorative elements like little figurines or a teeny garden chair and table or whatever strikes your fancy. “It’s a place you can do a little daydreaming, and it’s a great project for kids, too,” says Hachadourian.
Place your terrarium where it gets bright, indirect light. It’s a common mistake to give it direct sunlight, which will fry the plants when the light is magnified by the glass.
How to Water a Terrarium
Closed terrariums retain more moisture and seldom need watered because the water recycles within the terrarium. Open terrariums, where some of the water vapor can escape, need watered more often. “The biggest mistake people make with terrariums is overwatering,” says Hachadourian.
Heavy misting is typically all you need to water a terrarium. But keep an eye on moisture levels. If too much water is condensing on the inside of a closed container, open the lid and refrain from misting.
Most terrariums only need watered every few weeks or so, depending on its size and the maturity of the plants. You also can feed your plants minimally because you don’t want to push too much growth so that they quickly outgrow the space, says Hachadourian.
A sprinkle of slow-release fertilizer granules or a diluted water soluble fertilizer occasionally is all your terrarium plants need.
Best Plants for a Terrarium
The best plants for terrariums include anything that’s miniature and doesn’t require a lot of pruning to keep it in check. “You want plants that aren’t going to take over because then it loses its charm and just looks like a bunch of green leaves, instead of individual plants,” says Hachadourian. “If you choose the right plants, your terrarium can last for 15 or more years.”
African violets are happiest in bright, indirect light and high humidity. Make sure to prevent the leaves from touching the glass, however, or they will burn or become mushy. Plant them in the middle of the display for best results.
Sometimes called string of frogs, this charming plant will creep and climb in your terrarium. It loves high humidity, so it does particularly well in a closed terrarium.
Air plants actually are epiphytes that grow on tree limbs in the forest, absorbing water and nutrients through their leaves. You can display them on their own inside a glass globe, mounted on a piece of bark or stone.
Jewel orchids, which are terrestrial orchids that grow in soil, have beautiful striped foliage, which is more striking than their tiny flowers. As rain forest plants, they love moisture, so they’re quite happy in a terrarium.
Not actually a moss, this plant has soft, beautiful foliage. It’s nearly impossible to keep alive in the average home because it adores high humidity. This makes the terrarium the perfect environment for this charming plant.
With such a cute name, you can’t go wrong! Polka dot plant has pink, red or white spotted foliage. It’s slow-growing and loves humidity, making it an ideal terrarium plant. Prune it if it becomes too leggy.
These colorful plants with their gorgeous striping or splotches can be fussy to grow outside a terrarium because they love humidity. They make colorful additions to larger terrariums.
The colorful foliage of fittonia is slow-growing and stays compact, making it a great terrarium plant. It has interesting patterned foliage in shades of white, red, and pink.
With its delicate, lacey foliage, this fern has personality plus. It’s fussy in most dry interior environments, but it will thrive in the humidity of a terrarium
With its unique nest shape, bird’s nest ferns adore humidity, so they’ll be right at home inside a terrarium. They also like moist soil, but they don’t want to stay soaking wet.
There are so many different kinds of begonias! Miniature begonias are absolutely magical in a terrarium, with their beautifully patterned leaves and various forms. They love consistent moisture, so a terrarium is just right for them.
This delicate wispy-looking fern is perfect for terrariums because it loves high humidity and can be tough to grow outside this type of environment. It also has teeny thorns so wear gloves when handling.
Marc Hachadourian is the director of glass house horticulture and senior curator of orchids at the New York Botanical Garden. He is also the author of the book Orchid Modern.
Expert consulted: Marc Hachadourian
