January 27, 2012

by Beth Ellis,
Victoria County Master Gardener

edited by Charla Borchers Leon,
Victoria County Master Gardener

Editor's note:  This is the last of a two-part series on terrariums. See Part I HERE ~
Gardeners' Dirt
Clear glass or plastic containers of most any size and shape are suggested over colored glass ones for terrarium plants to receive the full spectrum of light. The use of lids is optional depending on the kind of plants.
Supplies for a terrarium with tropical plants include pebbles, moss, activated charcoal, then soil that does not retain too much moisture with plants that require medium to low light plus small knickknacks (rocks, shells or small animal), if desired. Succulent plants, on the other hand, are planted directly into fresh sand instead of the first four layers.
Terrariums with tropical plants should include a lid that helps retain moisture indicated by moderate condensation on the upper part of the glass. Once established, airing, watering and glass cleaning should be done as needed monthly.
This planted terrarium is complete with eight layers, including adequate light and proper watering.
My experience with terrariums is new, and, frankly, I never gave much thought to them until researching this article. In the spirit of avoiding the "do as I say, not as I (don't) do" thing, I decided to make a few terrariums of my own, and in the process discovered just how enjoyable they can be.

Give terrariums a try - they're fun, the results are whimsical and pretty, and it's a good way to liven up your home during bleak winter days.

Usable Containers

To start, choose clear glass or plastic containers so plants receive the full spectrum of light.

For this reason, use colored glass or plastic sparingly. Containers can range from mini to grand and be all sorts of interesting shapes.

Use of lids is dependent upon the plants inside (tropical plants - yes; succulents - no).

You may want to sketch a planting layout ahead of time, or just wing it - do whatever suits you.

Include Up to 8 Layers

For tropical terrariums you'll need pebbles, sphagnum or Spanish moss, activated charcoal, potting soil, props and humidity-loving plants.

For succulent terrariums, use only sand, so skip Layers 1-4. Avoid beach sand (who knows what's in it)?
Instead, use clean decorative sand found at florist, hobby and aquarium shops.

Layer 1 - Pebbles. Use one half to 1 inch of pea gravel, aquarium gravel, or something similar for drainage.

Layer 2 - Sphagnum or Spanish Moss. Squeeze out dampened moss and add as a permeable barrier to keep upper layers from muddying up the pebbles.

Layer 3 - Activated (aquarium) Charcoal. Add a handful to filter the environment in your terrarium. It can be dusty, so add it carefully to avoid dirtying the glass.

Layer 4 - Potting Soil. Avoid brands with moisture retentive additives, as they can make your terrarium too wet. If soil is very dry, dampen and work it with your hands. It should be very slightly moist, not soggy. Make this layer between 2 to 4 inches to prevent disturbance of lower layers when installing plants.

Layer 5 - Plants.
For tropical terrariums, use small plants requiring low to medium light. Plants with multiple stems can be divided to obtain the right size for your container. Use combinations of plants with different leaf shapes, colors and textures to create visual interest. Good choices include mosaic plant, aluminum plant, artillery fern, polka-dot plant, Boston fern, as well as many others.

Divide plants as needed, and carefully remove excess potting soil from around the roots. Dig hole in the soil with a spoon, and place the plant at its original soil level.

For succulent terrariums, scrape off the top layer of soil from around the base of the plant and replace it with sand when planting, to prevent a dark ring of soil from showing.

Layer 6 - Props.
This is a great opportunity to incorporate small knickknacks. Crystals, shells, toy animals, rocks, fossils, ornamental moss - you name it.

Layer 7 - Light Needs.
Light needs of plants determine terrarium placement. Low light plants allow placement further away from windows, medium light plants dictate a closer spot. Remember, more light equals higher temperature - so don't place terrariums in direct sunlight. Otherwise, your plants will cook.

Layer 8 - Watering.
After planting your tropical terrarium, add a little water, put the lid in place, and keep an eye on it for a few days. Monitor condensation - water droplets should appear on the upper part of the glass. If condensation is so heavy it obscures the view, it's too damp - take the lid off and let the terrarium air out. When adding new water, occasionally use some one-fourth strength fertilizer if plants need it. Once established, a monthly, or as needed, airing, watering and glass cleaning will prove beneficial.

For succulent terrariums, water every couple of weeks, occasionally adding one-fourth strength fertilizer if needed.

Last Thoughts

Remember to monitor the condensation in your terrarium - if it's too wet, take the top off and air it out. If plants aren't doing well and water is not the issue, then light (either too much or too little) is likely the cause. Remember that more light equals more heat, so be careful your plants don't accidentally turn into steamed vegetables. Also remember that if a plant gets too big, it's OK to trim or trade it out. If a plant doesn't survive, replace it. If you get tired of how your terrarium looks, change it up.

And last but not least, remember that if plants way back in the 1830s could survive being sealed up in Wardian cases for six months at a time on the decks of storm tossed, salt-sprayed sailing ships - surely they can survive living in a terrarium in the sedate environment of your home in 2012.
"Terrarium Craft:  50 Magical Miniature Worlds" by Amy Bryant Aiello and Kate Bryant, Timber Press ~
"The New Terrarium:  Creating Beautiful Displays for Plants and Nature," by Tovah Martin, Clarkson Potter Publishing ~


~ How To Make A Terrarium @ ~

Note: Lots more information and images are on the Web; just do a keyword search and explore.
The Gardeners' Dirt is written by members of the Victoria County Master Gardener Association, an educational outreach of Texas AgriLife Extension - Victoria County. Mail your questions in care of the Advocate, P.O. Box 1518, Victoria, TX 77901; or, or comment on this column at