What Dwight Started

He was a meeting speaker in the early days of our new garden club. He had been an expert in terrariums and a grower and shipper of terrarium plants in the big terrarium boom of the 1970's. He had us each bring an empty wine bottle and he brought the plants and the soil and my kids and I took to it like ducks to water. We still have a few from those days, and while some didn't quite make it, we just keep making more. Here's what I learned starting with that talk at garden club by Dwight Lund.

We are talking about a closed nearly sealed terrarium here, not some giant brandy snifter with a wide open top. If it isn't closed, it is just a dish garden. And those decorative glass paneled miniature greenhouses don't count either, unless the edges of the glass panes have all been caulked to seal them. With their panes left loose, they lose too much moisture to count as true terrariums. Yet a terrarium is not totally sealed either, as it might require some tweaking and at some point, a bit of interior glass cleaning.

Selection of the container is the first step. It needs to be of clear glass to allow light in. It needs to be able to be closed. Wine bottles can be closed with a shooter marble. Larger bottles can be closed with larger marbles and large ball bearings. Canning jars with modern ring lids work, as do the older and reproduction ones with the glass lid hinged on with wire. Lidded candy and cookie jars and apothecary jars work. If you use something like a wine bottle that would have ended up in the garbage or something used from the resale shop, that would be a better thing than purchasing something.

The container needs to be clean and DRY so plan ahead. It is more trouble than it is worth to plant into a container with any moisture in it, because the soil sticks to the edges and makes a mess. Wash it and leave it open to dry well in advance of planting day.

You will need a tool for poking around in there. Make it first and have it ready instead of frantically scrapping about mid-planting in desperate search for something. Chopsticks and wooden or bamboo skewers work if your container is small enough. If your container is larger or if your container has walls that angle out from the top very much, you need a bendable tool, and the very best thing for that is a disassembled wire coat hanger. Cut off the twisted part and use the lower straight parts. Unbend the corners and reach one end in all the way to the farthest corner of the bottle. Bend a little U in the very end to use as a tiny shovel. Leave a few inches at the top to hold onto, bending the end into a handle if there is enough. Make another curved one that reaches the walls of the terrarium if needed.

Dwight taught us to use a bit of gravel in the bottom, then some charcoal, then a bit of soil. This is how we all did it in the '70's but my experience and science I have read tells me otherwise. The gravel serves no purpose in a terrarium because there should never be so much water that it needs to drain away. It looks cool to have layers, so go ahead if you want, and use sand or gravel or stones but know it is only for looks, not function. Charcoal is another matter. Myth has it that it absorbs odor, but who cares in a sealed terrarium? It is alkaline, hence the statements that it 'sweetens' the soil. But most potting soil is fine as it comes. Some things I have read state that its slight alkalinity keeps mold from growing, and if that is the case, you would want it on the surface. This is horticultural charcoal, little 1/4" or smaller irregular granules and not the same at all as charcoal briquettes. Don't even try to crush a briquette - it is not the same stuff. If you are going to be careful about watering and monitoring, this will not be needed anyway. Mold grows when it is too moist in there.

Soil can be anything of quality. Dirt from under mature trees, from under the mulch or leaf litter, as long as it doesn't have chemicals from the lawn or from colored mulch. It can be potting soil, but look before you buy. The soils that have styrofoam in them are just plain ugly and the styrofoam serves no purpose other than to lighten the soil for shipping. Perlite is a crunchy granular porous material used in soil that is too bright white for my taste. Vermiculate is greyish silvery layered substance and is fine. You need far less than you think. The plant in your terrarium is not going to grow very aggressively and just a tiny bit of soil is plenty. In a wine bottle, you will need about an inch and a half of soil. In a quart jar, an inch might be plenty. In a 5 or 10 gallon glass carboy, those bottles that water cooler water used to come in, about 3 inches is plenty.

Plant selection is key to success. The plant should have a mature height that is less than your container. It should be a plant that likes high humidity. Cactus are often recommended since they do not need much water, but they are prone to rotting in high humidity. If the soil has enough water for their roots, there will be too much evaporated into the air in the jar for their tops, which are suited to a high evaporation desert. Air plants (Tilandsias) are often recommended but they too will rot in a too high humidity environment. They grow in tree tops where there is a great deal of air movement. These plants are fine for open dish gardens, but NOT for closed terrariums. Some that I have had success with are creeping fig, whihc also comes variegated with white, small leafed ivies, a creeping foamflower, pellionia, muehlenbeckia, strawberry begonia, and those plants sold as shamrocks around St. Pat's day. They must be plants that grow in the humid rain forest or the humid wetland floor.

The plant must be able to be fit into your jar or bottle's opening. The leaves can be folded or rolled if they are soft, such as ivy or creeping fig, but more brittle leaves will just break, so choose a good match between bottle opening and plant leaf type.
The first step is to put the soil into the terrarium container. Try your best to keep soil off the glass. Make a paper collar or paper funnel to gently drop the soil through. It is easier to keep it off the glass than it is to clean it off later! Use your tool to poke it in place.

Then take your plant out of the pot that it came in and gently tease off as much soil as you can. Squeeze, shake, wiggle, poke, crumble, tug, prod, agitate, until you have freed each plant from the others and as much soil from the roots as you can. Once the plant is free from its neighbors and from much of its soil, it is ready to plant. If your container has a wide open top, such as a cookie jar or candy jar, wrap the loosely in a paper cylinder, stand the cylinder on the soil, and release the paper from the plant. If your container has a narrow neck, make a paper funnel of clean paper and work the plant through the funnel, rolling the leaves gently to fit them through. Once the plant is in the container on top of the soil, use a tool to move it to the side of where you want it to be planted. Use the tool to poke and scrape open a hole the size of the plant's roots. Poke the plant roots into the hole, and poke the dirt around the roots. Use the tool to shake the plant a bit to remove any soil that got on the leaves and to settle the soil and roots together.

Now for the watering. Stop here and take a deep breath. Say to yourself ten times "Less is better. I can add more later. It is really really really hard to get water out and really really really easy to add too much. Moderation is magnificent." Are you calm and restrained? If not, read that over again. You have been warned: DO NOT OVERWATER. Overwatering is the preferred failure method of most terrarium makers. Avoid being this cliche! So, if you are ready to begin watering SPARINGLY, take a look at your container. If it is a pint or quart jar or a wine bottle, you will need to drop in water by the teaspoonful. If it is a larger cookie jar or lidded jar, maybe tablespoons are more the ticket. If it is a five or ten gallon carboy, start with a quarter cup. Pour in that water and wait for it to be completely absorbed by the soil. If there still appears to be dry soil, try another spoonful. If there are not dry pockets, stop now. Put on the lid or stopper, and let it be.

If you got soil on the walls of the jar or container, DO NOT try to run water down the side to remove it. This is probably the biggest mistake people are tempted to make that leads to over watering. Use your tool to poke at particles, or if there is quite a bit of soil, use duct tape or strapping tape or packaging tape to tape some strong paper towel or a piece cut off a sponge onto your tool and use that to clean the glass.

If you have overwatered, you can try to absorb some of the water out with paper towel strips or cloth strips. Do not get yourself in a situation where you get paper towel or cloth stuck in there. So either tape it securely to your tool, or use a long enough strip that some of it sticks out the top to use to pull it back out after it has absorbed the water. It takes many repetitions of sponging water out to remove just a bit of excess, which is why I warned you so strongly to not overwater.

As for long term terrarium maintenance, keeping the moisture level right is key. The water in the bottle will evaporate into the air of the bottle and condense on the inside of the glass. If not very much condenses late in the day, you need to add a bit of water. Start with a few drops and add more if needed. Condensation should be on one side of the jar or just on the top third or so. If there is condensation all around the inside or if there is so much that the water runs in lines down the glass, there is too much water in there. You might be able to just open the jar for a while to let this evaporate out, but if it is seriously too much, you will need to absorb some out.

If the plant gets too large, and you can reach inside, you can prune it. This works for vining creeping plants, but not for plants that just get too tall. If the terrarium is a bottle and the plants have filled it, you may be able to make a hook in the end of your tool and pull some to the top so that you can clip it off.

If algae grows on the glass, you can use your tool with a sponge securely taped to it to rub it off. This is a tedious job that takes time and patience to avoid damaging the plants or to avoid losing the sponge in the terrarium. But is is a sure way to tidy up a messy looking mature terrarium. Remove the sponge and poke any dead leaves down into the soil.

With just a tiny amount of maintenance, your terrarium will survive for years and years, something that can't said of many other houseplants!