A terrarium is an enclosed growing system for plants – complete with soil and moisture. They were all the rage in the ’70s. And for good reason: They’re a great way to grow plants in a low-maintenance environment, and they last for years. Terrariums are easy to build, too. In just a few simple steps, you can create a lovely indoor garden to decorate your home or to give as a gift.

Terrarium at Philadelphia Flower Show

This interesting terrarium was found at the Philadelphia Flower Show.

Photo Credit: Mary Ann Patterson

Jar Terrarium

Empty jars make neat terrariums – especially for kids. This one took less than 30 minutes to make, but it’ll last for years.

Photo Credit: Mary Moore

Variety of terrarium cases

Hobby stores sell a wide variety of containers that can also be used to make interesting terrariums.

Photo Credit: Mary Moore

Terrarium plants

Look for interesting plants with neat colors, textures and variegation.

Photo Credit: Mary Moore

Terrarium gravel

An inch or so of drainage material is essential to terrarium plant health.

Photo Credit: Mary Moore

The first decision you need to make is the type of container can you want to build your terrarium in. You can choose between glass jars, aquariums, large funnels, large bottles, clear plastic soda containers, plastic jars… . Really, just about any watertight, clear container that’s deep enough to allow for the gravel, soil and plants will work. As long as it’s got a lid (unless you’re trying to grow a desert terrarium) it should be okay. The lid locks in moisture, creating humidity and condensation. If done correctly, your terrarium can remain sealed for years without additional watering.

Next, you need to gather your ingredients. Be sure to use a good, light potting soil instead of garden soil. (Garden soil is too heavy for terrariums and may not be free of disease or insects.) The potting soil you purchase will probably be a soilless mixture, which means it’ll contain perlite or vermiculite, as well as be light and able to retain moisture.

Of course you need some plants. It’s best to choose slow growers that don’t need a lot of direct sunlight (unless you’re doing a desert garden). Local nurseries or home stores often sell small houseplants that work nicely, with variegated foliage or small flowers. Consider ferns, slow-growing groundcovers, Venus flytraps or pitcher plants, too. Add further interest by including some tall, spiky plants (like lucky bamboo or dracaena) or some bushy plants that’ll spread slowly (like a fittonia or palm). For a lush, low-growing groundcover, think moss or lichen.

As always, select plants that have similar light, heat and water requirements. And make sure the plants are healthy before you buy them. (Look closely for signs of insects, mildew or mold.)

Don’t forget to also buy drainage material so your plants don’t sit in water and get root rot. Gravel is a good, inexpensive choice, and you can add a small amount of charcoal to it to prevent a sour smell from forming in the water. You can also use a lightweight clay product sold at pet stores for lizards, snakes or other pets that are kept in terrarium environments.

Now’s the time to put it all together. If this is your first terrarium, start with a large container and a simple planting plan. Just follow the steps below and see how easy and fun this project can be:

  1. Clean the container with soap and water. Dry completely.
  2. Place an inch of clean drainage material (rinse it first) in the base of the container. Smooth and level the surface.
  3. Place 2-3 inches of potting mix over the drainage material. If you’re using a large container like an aquarium, consider adding some topography by building the soil higher in some places to imply hills and valleys to add interest to your little landscape.
  4. Start planting around the edges and work your way into the center. Start with one of your bigger plants as the foundation of your terrarium’s landscape. Remove the plant from its container and massage the roots gently to encourage them to spread. Dig a hole about the size of the root-ball, place it into the ground, and cover the remaining exposed roots with potting soil.
  5. Add your remaining plants, carefully covering the root-balls and smoothing out the surface. If you have any moss, place it firmly onto the top of the potting soil.
  6. Add water. Remember you want the soil to be moist, but not soaking wet. Don’t fill the gravel at the bottom with water because the potting soil won’t be able to drain any extra liquid. If you overwater the container, try to drain out the extra liquid and keep the lid off your terrarium until the extra water evaporates.

With a few simple precautions, your terrarium should be able to maintain itself, possibly for years. Just be sure to keep the container in indirect light, because direct sunlight will overheat your container and injure the plants inside. You can use strong florescent lighting. Simply attach a florescent light to the aquarium lid or place your terrarium under a florescent plant light.

Finally, if you see a lot of condensation on the sides of the container, the plants may be too hot. Move your terrarium or shade it from its light source. If that doesn’t help, your terrarium might simply have too much water inside. Check the level of water in the drainage material for overflow, and open the lid to allow some evaporation.

As you enjoy watching your terrarium grow, make some mental notes on how you want to build your next one. And use your imagination. Every terrarium can be a unique experience!