Creating Terrariums with Tropical Plants

When I was in middle school and my family moved into a new home in Sugarland Run, in Virginia, the realtor gave my parents a housewarming gift of a large, foot high glass bottle of little plants. It was the first time I saw a terrarium, and I thought it was magical. A tiny, enclosed forest of tropical plants, where you can just imagine the trolls peeping through.

Now, with the advent of succulents, the word “terrarium” can mean sand-filled landscapes of succulents and bone-dry skulls. It also can be a singular tillandsia on white pebbles in a glass dome. There are many terrarium books on the market and if you flip through the glossy pages, you will see that anything is possible.

But to go back to the basics, to re-create that magical world, is actually very easy. It also is a great indoor project to do in the winter.

At the very least, you need the container, pebbles for drainage, potting mix, and the plants. You can use activated charcoal, moss, and decorations. A water mister with a stream option makes clean up easy and if the opening is wide enough for your hand to get through you should not need special tools.

Look around your house for a glass container. For beginners, it is easier to have one with a wide opening. It can be an open container or one with a lid; you can always add a lid. See if you have an old goldfish bowl, fish tank, or even a glass cookie jar. If you don’t have one, visit the local Salvation Army, Goodwill, flea market, or pet stores for cheap containers.

Purchase pea gravel and houseplant potting mix from the hardware store or nursery. You can get a large, heavy bag of pea gravel in the outdoors nursery section of Home Depot and Lowe’s or you can purchase a small bag where they sell houseplants. You can also purchase small bags of pea gravel at nurseries. The Fair Oaks location of Merrifield Garden Center has a bin where you can purchase pea gravel by the scoop.

Often the plants in the 2-inch containers are root bound so tease the roots apart.

Purchase a few small tropical plants, the type that are sold in plastic 2-inch containers. Make sure you look at the price of each one because when viewing from the top, they all look the same, but when looking at the price tag from the side, you may notice that some plants are three times more expensive than others. No need to purchase expensive ones.

Selecting plants for the terrarium is very similar to purchasing plants for containers in the garden. Think “thriller, spiller, filler.” Choose an upright plant, a mounding plant, and a trailing or creeping plant. Have an odd number of plants — 3 or 5. Create visual interest through different textures and colors. Also, think of how you can create more interest either with moss, decorative stones, or bark.

You can purchase bags of activated charcoal at the houseplant section of the hardware store or the nurseries. Activated charcoal has been treated at a very high temperature to be more porous and is used as a filtration system. It is supposed to remove impurities and prevent mold and mildew. The are just as many advocating the use of charcoal as those who say it is a waste of money. I use it when I am using a completely enclosed system.

Teasing apart one plant to get several.

You also can purchase sheets of dried moss. There are a few types available locally and more online, including live moss. Do not dig up moss from your garden. You could be bringing in insects, bacteria, and fungal organisms, which when placed in a terrarium, could “bloom” out of control.

When selecting the container and the plants, keep in mind the headroom – the space above the plants that is necessary for oxygen. Make the headroom about half the height of the container.

Step-by-Step Process:

1. Remove the plants from the containers and examine the root structure to see if a) they are root bound and b) you can easily divide the plant. Like plants you purchase for the garden, these may be root bound and must be teased apart before planting. Likewise, if you look where the growth is coming from, you may see that you can loosen and separate to have more than one plant. If you can get more than one plant but you only need one, just pot up the extras for a future terrarium.
2. For the plants you are going to put in the terrarium, moisten the root system by submerging in a mug of water.
3. Add a layer of pea gravel for drainage to your container.
4. Add a thin layer of charcoal, just to cover the pea gravel.
5. Add a layer of the potting mix. The depth will depend on the container and plants. Add enough to cover your plants’ root systems.
6. Insert plants with moist root systems.
7. Add more potting mix around plants, tamp into place with your fingers.
8. Add moisten moss if desired (moisten by spritzing with water). Tamp everything in place.
9. When you are satisfied with the placement you can either clean up now and wait to add the decorative pieces later or add everything now and clean up. I like to clean up and then let my terrarium sit for a few days so I can ponder if it is truly done or not. A terrarium is a work of art. You need to feel comfortable that you have made it the best it can be.
10. Clean by misting or squirting the foliage with water – just enough to get the soil off. Wipe the container’s sides with a paper towel. It is not necessary to water the plants, and you don’t want to inject too much water.
11. If there is a lid, put the lid on. The next day, if there is condensation, take the lid off, wipe the sides, and let the moisture evaporate to “dry” out a bit. Condensation is a sign of too much moisture, which may lead to fungal issues.
12. Place the terrarium in a warm area with bright light, not in direct light.

Terrariums are not watered often like houseplants. Theoretically the plants get enough water by being in an enclosed or partially enclosed environment and by being in proximity with each other. You should water when the soil looks dry, lighter in color, or the plants are wilting. Keep an eye on condensation and “critters.” If a piece of plant has died or is moldy, remove it.

Terrarium plants are not fertilized. You are not encouraging growth; you are encouraging a level of equilibrium, so the plant is able to obtain what it needs. In other words, you are creating a mini world of tropical plants.

Try making a terrarium this winter. This is a fun activity to do with your friends, garden club, or kids. They also make excellent gifts.