Plants That Live In Glass Houses

Thirty years ago you couldn’t go into a nursery, florist, garden supply shop, department store, supermarket or gas station without seeing one. Some were traditional, constructed in the Victorian motif, while others were new age and some were just antique Wardian cases. No matter where you looked there were thousands and thousands of them either in bowls, bottles or abandoned fish tanks. And guess what, they’re back ... terrariums. They make wonderful projects to work on with kids and a growing number of people are using them to house their rare and exotic frog collections. That’s right, frog collections.They were also the rage a couple of hundred years ago, but then they were called Wardian cases and they served an important botanical and economic function. These glass boxes were the structures that sailors, botanists and explorers put their treasured plants and cuttings in while their ships plied the seas on the long trip back to Europe. Inside the boxes the specimens stayed relatively warm and very humid, growing slowly if at all, but staying alive.

As a child you may have built a terrarium in school or at summer camp. For these you most likely used an old fish tank and local flora with the possible addition of a frog, toad or salamander. Along the way someone also discovered that with a few well designed tools a garden could be planted inside an old glass water bottle, then in glass globes, goblets and finally in plastic domes.

It’s very simple to build your own and it’s a great project to work on with children. All you need are some free or inexpensive materials, a few tiny plants and a bit of imagination.

By definition, terrariums are clear plastic or glass containers, usually with covers, filled with live plants. You can use your imagination to scout around the house to see if you have containers that can be made into terrariums, but the glass or plastic must be clear, not smoked or green. Glass jars, goldfish bowls, fish tanks, glass bricks, preserving jars, brandy snifters, apothecary jars ... all will do. If your container has no cover, make one by simply covering the opening with a piece of clear glass, plastic or Plexiglas.

Clean the container thoroughly, inside and out, to remove stains, smears, fingerprints and dirt. Use window cleaning liquid and a lint-free cloth or newspaper for the cleaning job. If you are using a container that has unusually curved sides or hard-to-reach corners, you may want to make a tool that will allow you to reach these spots. This can be done with a wire hanger or some spare wire from the garage. Once it is cleaned, allow the container to air out for several hours or overnight.

Next, line the sides of the interior of the container with green moss that you have collected from outdoors in a wooded area or use unmilled sphagnum moss from the garden supply store. This lining should run up the side of the container to the same height that you are planning to do your planting or slightly below. Now, using a funnel add enough course sand or fine gravel until it covers the whole bottom about 1 inch deep, over the moss.

Charcoal goes in next, but it should be washed first. The charcoal acts as a filter and freshener. Use either fish tank filter charcoal or horticultural charcoal or barbecue charcoal—NOT the quick-lighting type—that has been smashed with a hammer. Add a half-inch layer of charcoal on top of the sand.

Next, add potting soil—not the types with fertilizer added—or weed-free topsoil on top of the charcoal until it is about 2 inches deep. Be sure that the soil is moist, but not wet. As you add the soil, pat it with a long skinny stick so it packs down slightly and does not shift. Don’t make the soil flat. Make it uneven so there are small hills and valleys, just as there are in nature. Some rocks and sticks can be added later for effect, but don’t put them in until after the planting is done.

Decide what plants you want in your terrarium and plan on paper where they will go. Shy away from fast-growing plants, as they may overtake the landscape rather quickly. Retail garden centers and greenhouses often have a supply of small and inexpensive plants in cells or small pots that do particularly well in terrariums, but stay away from cacti and succulents unless you are planning to build a 1960s-type desert terrarium with more sand (often colored), less soil and no cover. You can also look online for lists of terrarium plants.

Make planting holes in the soil with a stick exactly as marked on the plan. Slip the plants out of the pots and into the holes and use tongs if it’s difficult to reach the holes. Gently pack the soil around the plant and its root ball. Don’t overdo the planting. The plants will grow larger and in some cases quickly. Try to avoid the need to get back into the planting area in a month or two to remove an overgrown mess. A properly planted terrarium should last at least a year without replanting or major maintenance.

Water the terrarium thoroughly (except the desert) after all the plants are in, using a watering bulb or spray bottle so that all of the soil and plants are moistened … not drenched. Replace the cover and you will rarely have to water again, but if the soil becomes dry, simply use your watering bulb or spray bottle and sparingly add more water.

Put the newly planted terrarium in a light, but shaded spot until the plants root. Then move it into a brighter spot, but never in an area where the sun or a source of direct heat (radiator or hot blowing air) will hit the structure, as it will quickly bake. You’ll probably never need to fertilize, as your original soil will have enough nutrients to sustain growth for many months.

Explain to children that the terrarium works the same way that nature does, only in a smaller way. Using oxygen, carbon dioxide and water for plant growth, you have created a self-contained and constantly repeating life cycle. The plants use the carbon dioxide in the terrarium’s air and the water in the soil, plus the light, to live. In turn they give off oxygen and water into the air, and the cycle is repeated. Keep the cover on and you have an unbroken chain, your little piece of nature under glass. Sixth graders may also tell you that it may be a great way to explore thy hydrologic cycle as well. Several summers ago I found a very old Coke bottle that had been partially buried horizontally in some soil. I gently lifted it out, thinking it might be collectible, and much to my surprise, inside it was some dirt and a growing, thriving fern. A terrarium.

If you’re interested in learning more, just Google “terrariums’” and I hope you’ll try to get a child involved in this as well. A terrarium is a great place to grow and watch a range of “carnivorous” plants that are being sold in most garden centers these days. And if you’re lazy and thrive on nearly instant gratification, you can buy complete terrarium kits from the White Flower Farm ranging in price from $33 to $175. Keep growing.