An ode to the original terrarium, this glass house is full of life and color.
The Victorian Age brought with it an explosion in gardening. The romantic vision of nature blossomed as more people lived in urban environments, isolated from the natural world. In the late 1820s an English doctor named Nathaniel Ward came upon the idea for a miniature version of the large glasshouses that were then popular. His miniature glasshouse, a precursor of today’s terrarium, was called a Wardian case. Suddenly there was a way for the avid botanists of the time to safely transport exotic plants home from around the globe.
There are two types of terrariums: open and closed. Closed terrariums are covered and have high humidity. For a closed terrarium, choose plants that love humidity and that will do well in bright indirect light (closed terrariums should not be placed in direct sun; they get too hot). Open terrariums can tolerate a little bit of sunlight, but not too much, as the glass can act as a magnifying glass and burn the plants. For an open terrarium, choose plants that like more sunlight, like cacti and succulents. When you’re deciding which type of terrarium to use, consider the light conditions in your home.
African violets, discovered in 1892, are the perfect plant for a closed terrarium, because they thrive in humidity. In their native habitat, the Usambara Mountains of East Africa, African violets enjoy 70 to 80 percent humidity. Other great plants you could use in this closed terrarium are hypoestes or pilea, or a fern.
I used insect specimens to represent the live hatching butterfly that many original closed terrariums housed. Eventually the butterfly and beetle specimens will decompose in the humid air of the terrarium. To slow this process I’ve coated the insects with a clear spray paint. It may not protect them completely, but it will slow the absorption of moisture and prevent mold, giving them more durability in the humid conditions of the terrarium. Do not let the bugs come into direct contact with the moss—it will create mold on the insects. In this project I’ve mounted the butterfly on a small piece of wood so that it doesn’t touch the moss, and I’ve positioned the beetle on a pin half an inch up from the moss.
MAT E R I A L S
- Wardian case with a removable top and hatch for ventilation and a plastic tray at the bottom of the case (A)
- Crushed gravel (B)
- Chipped charcoal (C)
- Sheet moss (D)
- Potting soil (E)
- 4-inch African violet (Saintpaulia ionantha) (F)
- Haircap moss (G)
- Cushion moss (H)
- 1 or 2 pieces of found wood, about 3 to 4 inches long with a 1-inch diameter (I)
- 2 to 3 mounting pins 3 insect specimens (J)
- Scrap paper Clear spray paint (use a glossy one for the beetles) (K)
Take the top off the Wardian case.
Pour a 1-inch layer of crushed gravel into the tray.
Cover the gravel with a thin layer of charcoal, which will filter the water and reduce odor.
Press the sheet moss over the charcoal—it will function as a barrier between the soil and drainage material.
Layer the potting soil on top of the sheet moss.
About one third of the way in from the left side pull the sheet moss back to make a hole for the African violet in its pot.
Place the African violet, still in its pot, into the depression. (I leave the African violet in the plastic pot for three reasons: African violets tend to not bloom if they’re overpotted—they tend to bloom better if they’re pot-bound. A general rule of thumb is that the pot should be one-third the size of the span of the plant. Also, I like to be able to water the African violet separately from the moss. And last, if the plant gets more light from one side I like to be able to rotate the plant so that its exposure to light and potential growth is equal.)
Place the haircap moss around the African violet’s pot so that the pot is no longer visible. Push the moss down so that it makes contact with the soil.
On the other side of the terrarium place the cushion moss, using more in some places to give the topography some variety by making smaller and larger mounds.
Position the pieces of wood in the gravel on the right-hand side, so they stand just short of vertical.
Push a mounting pin through a beetle specimen and place the beetle on a piece of paper. Spray the insect with the clear spray paint, being careful to cover the whole specimen, especially its bottom side. Let the spray paint dry and repeat. I did not spray my butterfly because of the delicate nature of its wings. I’ve had it in a terrarium for a year and it is still in perfect shape. Repeat with the other insect specimens.
Once the insects are completely dry, place them in the terrarium. Pin them securely to the wood or moss. If you mount them on the moss be sure to leave a half-inch gap between the beetles and moss to help prevent deterioration from mold.
A closed terrarium retains moisture and recycles the water for a long period of time. You want to have some moisture in the terrarium, but not so much that there is a buildup of moisture. A closed system needs very little water. If you see water droplets building up on the inside of the glass you have overwatered. If the terrarium walls have more than 25 percent condensation, remove the cover until the walls clear. You may have to do this more than once. In a closed terrarium, there should be only occasional clouding. If you begin to get any rot or mold you have overwatered and will need to replace those plants and insects. The presence of mold or mildew indicates that one of three things is wrong: the terrarium may contain too much water, air circulation is poor, or you are using plants that do not do well in closed terrariums. Remove infected plants immediately and correct the environment by letting the terrarium dry out or by increasing its air circulation. The moss will go through an acclimation phase, during which it may need more water than normal. It should establish itself within a few months. Once the moss has adjusted to its new home spritz it with a sprayer two to three times a week. (How often you’ll need to spritz it will vary depending on your location, temperature, and how often the lid is open.)
Water the African violet separately with a watering can that has a narrow spout using lukewarm or warm water. You will know it needs water when the soil is dry. You can use your finger to feel if the soil is moist. The best way to water is to remove the African violet from the terrarium and place it in a saucer. If using a watering can or faucet to water from the top, avoid getting water on the leaves. Let the African violet sit in the saucer with the water for a half an hour to an hour. Once the plant has absorbed all the water it needs return it to the terrarium and discard the excess water. African violets should be allowed to dry out between waterings.
Closed terrariums should not be placed in direct sun, as the temperature inside will get so hot the plants will melt. African violets and moss do well with bright indirect light. They do well near a window, but out of direct sunlight. Watch out for cold wintertime night temperatures—if it is a cold night, take the terrarium away from the window and only return it once the morning sun has warmed the space.
Remove the cover of the terrarium for a few hours every week, or open the vent to provide some air circulation. Pinch off any old blooms and their stems to encourage new growth. If you notice any mold or rot clean it out immediately so that it doesn’t spread, and try to get the terrarium back to an optimal level of humidity and moisture. Keep it away from vents, radiators, air conditioners, and fans to avoid drafts and sudden temperature changes. You may need to periodically clean the glass, for your benefit and the plant’s, because dirty glass can diffuse the amount of light the plant is receiving. If you develop any pests or insects cut out infected areas and spray with insecticide.
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