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#1 ·
Courtesy of http://muextension.missouri.edu/xplor/agguides/hort/g06520.htm

Terrariums
David Trinklein
Department of Horticulture


A terrarium is a tightly closed clear glass or plastic container filled with small plants (Figure 1). It also has come to mean an open, transparent container for growing and displaying plants. Terrariums are most useful for small plants that do not adapt well to normal home atmospheres. When properly planted and located, they provide a way to grow many plants with minimal care.

Brief history
Transparent containers for growing plants date back to at least 2,500 years ago in Greece. But in the United States, terrarium culture is believed to originate in New England, where housewives placed squawberry (partridge berry) in hand-blown glass bowls.

Invention of the terrarium as we know it is credited to Dr. N. B. Ward of London. Ward was interested in growing many types of ferns in his backyard but had not been successful. While studying a sphinx moth emerging from the chrysalis he had buried in moist earth in a closed bottle, he was amazed to see a seedling fern and some grass growing inside. He watched them grow for four years, during which time not one drop of water was added, nor was the cover removed.

Ward continued his observations with other plants in containers, and in 1842 published a book called On the Growth of Plants in Closely Glazed Cases. This led to development of "Wardian Cases," which were large, enclosed containers for growing delicate plants in the home or transporting precious plants over long distances. The terrariums most often used today are small ornamental versions of the Wardian case.

Planning a terrarium
Closed, open or dish garden?
Open terrariums provide higher humidity for plants than do dish gardens, but closed terrariums retain more humidity than either of the other container types. The open terrarium and dish garden require more frequent watering, but danger of disease buildup is reduced.

Before beginning your terrarium, decide whether you prefer a woodland, tropical or desert theme. Keep in mind the temperature and light conditions in the location where you plan to place the terrarium. Select plants that suit the location.

Containers
A terrarium container must be made from clear glass or plastic. Tinted or cloudy glass greatly reduces light transmittance and interferes with plant growth. As long as it is clear, almost any type of container may be used: empty fish bowls, fish tanks, brandy snifters, old glass jars, jugs, bottles. There also are containers specially designed for use as terrariums.

All closed containers should have transparent covers. Containers with small openings also are quite satisfactory. Containers with large openings without covers can be used but will require more frequent watering to maintain the high humidity needed by some plants. However, open terrariums are drier and less subject to disease. Containers without high sides are suitable for dish gardens and need not be transparent.

Growing medium
The growing medium for terrariums must be clean, well drained and high in organic matter. Potting soils sold at garden centers and nurseries where plant supplies are sold are sterilized and ready for use. Prepackaged peat-like mixes also are excellent choices.

To prepare your own soil, mix one part peat moss with one part rich garden soil. Make sure the soil is moist before sterilization. Place it in an oven at about 200 degrees until the soil is thoroughly heated for 30 minutes. The exact time needed depends on the quantity of soil. Cover the soil with aluminum foil to prevent excess drying during heating. Spread the soil to cool on clean papers with clean tools. For planting, the soil should be moist enough to cling in a ball when it is squeezed tightly.

Adding fertilizer is not necessary, since plants in terrariums should not grow rapidly. If you know the soil used has exceptionally low fertility, light fertilization with a houseplant fertilizer may be done after plants are established.

Plants
Many plants are suitable for growing in terrariums. Plants that have a low and dense growth habit usually are best. Larger plants are often used. They are kept small in terrariums by cutting back the tips.

Don't mix plants requiring widely different conditions. Succulent plants and cacti are less desirable for terrariums, since moist conditions promote rot. Don't mix desert plants with moisture-loving tropicals.

The table found at the end of this page lists some plants suitable for terrarium or dish garden use, along with some of their cultural characteristics. It is designed as an aid in selecting plants with similar cultural needs. They are listed alphabetically by common name. Since there is variation in common names, more than one may be given, but each plant is listed only once. The following points are described in the table:

Height
Since low plants are preferred, more emphasis is placed on small plants. They are divided into three size groups. Some of these are creeping or climbing vines that may grow tall, but with limited height in the terrarium they form a groundcover. Most plants listed in the "over 12 inches" category need occasional cutting back to be kept low.

Light
Most plants listed are in the "medium" light category and require good light near a window, or perhaps less light from a window supplemented with artificial light. The terrarium should be placed within several feet of a bright window, but not in direct sun.

Few plants tolerate "low" light for extended periods. Those listed for "low" light will tolerate a location no more than about 10 feet from a bright window.

"Bright" light means a location close to a window, often in direct sun, as for a grouping of cactus in a dish garden. Do not put closed containers in full sun.

Container
The true terrarium is tightly closed. Most plants require high humidity. Plants suitable for this condition are listed as "closed."

An "open" container is one with high sides, generally at least as tall as the plants contained. The opening at the top is not covered. Plants not needing high humidity can be used.

"Dish" refers to a planting in which a container is used with sides that are lower than the plants, so that the entire planting is subjected to normal conditions in the room. Plants tolerating low humidity are most suitable for this type of planting.

Temperature
"Warm" in this case refers to normal home conditions. Most tropical plants are suited for common house temperatures. At night, 65 degrees is ideal; day temperatures normally should be about 10 degrees higher.

"Cool" is a designation that primarily fits woodland plants in woodland terrariums. These plants should have nighttime temperatures about 50 to 55 degrees. In the home these temperatures may be difficult to find, but placed on a window close to the glass, with a drape pulled behind them at night, a pocket of cool air will develop during the winter. Day temperatures also should be cool but are not as critical.

Comments
This section lists only conditions or characteristics peculiar to the plant indicated.

Tools
Only a few tools are necessary for planting the terrarium. Long sticks, either bamboo or 1/4-inch dowling, will be most useful. The appropriate length depends on the height of the container to be planted. They can be used to dig holes, move items and support plants while they are being planted.

Household scissors will be helpful for pruning plants before they are planted.

A large kitchen spoon will be helpful in placing soil and drainage material in the container. If a container with a very small opening is used, make a funnel from paper or aluminum foil for placing soil into the container.

An atomizer or bulb-type sprayer will be useful for watering the terrarium. A kitchen bulb baster may be used for watering hard-to-reach spots.

A stick with a wire loop on the end will be helpful for lowering plants into large containers with small tops.

Accessories
Rocks, gravel and other natural materials provide pleasing accessories in designing terrariums. Sticks, wood, seed pods or bark are possible choices. Ceramic figures, frogs, mushrooms or snails suggest a natural setting. The materials added are a matter of individual taste. However, avoid too many accessories, or those with vivid, unnatural colors. Care should be taken not to introduce insects or disease with the accessories.

Other uses for the terrarium
Closed terrariums, with high humidity, make ideal propagation units for a few cuttings of houseplants. The idea also may be used to keep houseplants during a short vacation period. Plants can be placed in large containers or plastic bags with the top closed. They should not be placed in direct sunlight, or overwatered, but can normally be kept for 2 to 4 weeks in this way.

Assembling the terrarium
Design
Combine plants for variation in size, color and texture. Since terrariums usually are viewed from one side, the soil should be sloped for viewing from that side. Plants also should be arranged so that taller plants are toward the back. Use rocks, sand, wood and other natural materials to create cliffs, rock ledges, dry stream beds or lush tropical forests. Hills and valleys will make the scene more interesting than a flat surface.

Prepare the container
Before planting sterilize the container by washing it in hot, soapy water and rinsing thoroughly. Make sure the container is dry before planting. If you use a commercial glass cleaner, such as one containing ammonia, allow the open container to air for several days before planting.

Add drainage material and soil
In general, about one quarter of the terrarium's volume will be used for soil and drainage material. These can easily be added with a spoon, funnel or other convenient tool.

Drainage
Charcoal and pebbles should be placed in the bottom of the container for drainage. These may be mixed together, but the charcoal usually will be most effective if placed in a 1/2-inch layer above the layer of gravel, crushed pots, marble chips or other drainage material. Sphagnum moss, placed over the layer of gravel and charcoal, prevents soil from sifting into the drainage area.

Growing medium
Next, add the growing medium. It should be slightly moist so that dust is not stirred up, but not so moist that it is muddy and sticks to the sides. For most containers, a minimum thickness of 1-1/2 inches is necessary to provide sufficient volume.

Adding plants
Before adding the plants, arrange those selected for use in an open area about the size of the container. This will give you some idea of relative sizes and textural patterns. A low, coarse-textured plant is often desirable for a dominant focal point near the front. Don't build a collection of variegated or unusual plants. They compete with each other and don't give a unified pattern.

If there are disease concerns, enclose the plants to be used in plastic bags for about two weeks before planting in the terrarium. If any diseases are present, they normally will become visible on the foliage or stems. It is essential that tightly closed terrariums not be exposed to diseases.

To assemble the terrarium, take the plants from their pots and remove extra soil to expose the roots. Trim off any leaves that are yellowed, damaged or show any indication of disease or insect damage. Trim off some roots from plants that were extremely pot bound.

Promptly place the plant in the container, so that the exposed roots do not dry. In the closed container, try to keep foliage from touching the sides of the container. Leaves touching the glass will collect water and be more subject to rot.

Plants may be placed in a deep container using long slender tongs or a stick with a wire loop on the end. Deep containers with small openings will require considerable patience and practice in planting. For such containers, it is a common practice to wrap the plant in a piece of paper for protection before inserting it through the small opening. The plant is unwrapped and the paper removed once the plant is in the container. This also will help keep the inside of the container clean. Holes can be dug in the planting medium with a pointed stick before inserting the plants. After the plant has been inserted in the hole, fill in with soil and tamp it firm. A long stick with a cork fixed on the end makes a good tool for lightly tamping the soil. After the plants have been positioned, add gravel, sand, moss or other materials to give a finished appearance. Accessories also may be added at this time.

After planting
After planting, mist over the plants to wash off any growing medium that sticks to leaves or sides of the container. If the medium was properly moist at planting, no heavy watering will be necessary. The water misted over the leaves is adequate to settle the medium. Don't cover the terrarium, and repeat the misting after one day. Allow the container to remain open until the foliage is thoroughly dried. Then, if the terrarium is the closed type, apply the cover.

Watch terrariums closely for the first weeks after planting. It is at this time that diseases often get started. Any leaves that die or plants that begin to rot should be removed promptly before the problem spreads to other plants. Rots often are associated with too much moisture. If rot develops in a closed terrarium, remove the cover to allow more drying. If a fungus seems to be spreading from a plant through the growing medium, it may be beneficial to remove a portion of the medium in the infected area and replace it. Application of a general fungicide also may help to reduce spread of a disease.

In most cases, after a few weeks the terrarium is established and the threat of disease is reduced. Continue to watch for fallen leaves, however, or any plant parts that begin to decay.

Care of the terrarium
Watering
The closed terrarium normally will not need water for 4 to 6 months, or when fogging on the sides stops, or when plants wilt. Open terrariums need watering occasionally, but not as frequently as other houseplants. A dish garden, unless it is the desert type, will need frequent watering. It is important that waterings always be light. Since there is no external drainage, heavy waterings result in standing water in the gravel and charcoal, which encourages root diseases. These materials may help overcome occasional light overwaterings, but frequent heavy watering will inactivate the system. When watering the closed terrarium, don't replace the cover until wet foliage has dried.

Caution
Never overwater. Excess water is almost impossible to remove; better a little too dry than too wet.
Light
A terrarium, open or closed, should not receive direct sunlight. The dish garden, however, which contains plants needing bright light, may be placed in direct sun. Direct sunlight on a closed or tall, open container will cause heat buildup that will injure most plants. Most plants suitable for terrariums don't require extremely bright light, but do well in good light. If the terrarium is to be located where there is low light, add artificial light. A 100-watt bulb placed close to the terrarium or fluorescent tubes placed over the terrarium will be helpful. Where outside light is poor, add artificial light up to 16 or 18 hours each day.

Plants receiving light from a window gradually will face that direction. To keep the terrarium attractive from the desired view, turn it occasionally to keep the plants growing normally.

Pruning
Many plants in a terrarium will gradually outgrow their limited space. A little trimming quickly brings them into bounds, and often promotes side shoots that fill out plants. Pinching out tips before plants become too tall results in better growth than severe cutbacks. Be sure to remove all vegetation trimmed from the terrarium.

Fertilization
Since plants in terrariums should not grow rapidly, terrariums seldom need fertilizer. Don't plan any fertilization for at least a year after planting. If after the first year the plants are yellowish and seem to lack vigor without any other apparent problems, a light fertilization may be necessary. Use a water-soluble houseplant fertilizer at about one-fourth the rate recommended for normal houseplants. Do not allow any of this fertilizer solution to be left on the foliage.

Other care
Although a terrarium is designed for growing plants indoors with minimum care, it is not an inanimate object. Some plants will thrive, others may die. Occasionally it will become necessary to remove certain plants or add others. When adding plants, take all precautions described for planting the new terrarium. It is always possible to add new problems when adding new plants.

Favorable conditions for terrarium plants

African violet, Saintpaulia spp.
1 to 6 inches high
Medium light
Open, dish containers
Warm temperature
Must have good drainage


Airplant, Kalanchoe pinnata
Over 12 inches high
Medium, bright light
Open, dish containers
Warm temperature
Prefers full sun


Aluminum plant, Pilea cadierii
6 to 12 inches high
Medium light
Closed, open containers, dish containers
Warm temperature
Gets leggy in poor light


Ardisia, Coral berry, Ardisia crispa
Over 12 inches high
Medium light
Closed, open containers
Warm temperature
Very slow grower


Arrow-head plant, Syngonium podophyllum
Over 12 inches high
Medium light
Closed, open, dish containers
Warm temperature
Fast growing climber


Artillery plant, Pilea microphylla
6 to 12 inches high
Medium light
Closed, open, dish containers
Warm temperature
Grows fast, may need pruning


Asparagus fern, Asparagus plumosus
6 to 12 inches high
Medium, bright light
Open, dish containers
Warm temperature
Good drainage. Low light causes leaf drop


Baby tears, Helxine soleirolii
1 to 3 inches high
Medium light
Closed, open containers
Warm temperature
Vigorous ground cover


Begonia, Begonia spp.
Over 6 inches high
Medium light
Closed, open, dish containers
Warm temperature
Many types


Bird's Nest Sansevieria, Sansevieria trifasciata hahnii
3 to 6 inches high
Low, medium, bright light
Open, dish containers
Warm temperature
Very tough plant


Bloodleaf, Iresine herbstii
6 to 12 inches high
Bright light
Closed, open, dish containers
Warm temperature
Pinch back occasionally


Bunny-ears cactus, Opuntia microdasys
Over 12 inches high
Bright light
Open, dish containers
Warm temperature


Chinese evergreen, Aglaonema spp.
3 to 6 inches high
Low, medium light
Closed, open, dish containers
Warm temperature
Very durable. Can be cut back


Club moss, Lycopodium spp.
3 to 6 inches high
Medium light
Closed containers
Cool temperature
Woodland plant


Creeping fig, Ficus pumila
1 to 3 inches high
Medium light
Closed, open, dish containers
Warm temperature
Forms dense mat, clings to rough surface


Croton, Codiaeum variegatum
Over 12 inches high
Bright light
Closed, open, dish containers
Warm temperature
Foliage colorful


Devil's ivy, Pothos, Epipremnum aureum
Over 12 inches high
Medium, bright light
Closed, open, dish containers
Warm temperature
Variegated foliage, climbs


Dwarf gloxinia, Sinningia pusilla
1 to 3 inches high
Medium light
Closed, open containers
Warm temperature
Very dainty. Keep warm


Dwarf natal plum, Carissa grandiflora nana compacta
6 to 12 inches high
Medium light
Open, dish containers
Warm temperature
Easily pruned


Dwarf pomegranate, Punica granatum nana
6 to 12 inches high
Bright light
Open, dish containers
Warm temperature
May need pruning, Fruits in bright light


Earth stars, Cryptanthus spp.
1 to 3 inches high
Medium light
Open, dish containers
Warm temperature
Foliage may be colorful


Emerald Ripple, Peperomia caperata
3 to 6 inches high
Medium light
Closed, open, dish containers
Warm temperature
Avoid overwatering


English ivy, Hedera helix
Over 6 inches high
Medium light
Closed, open, dish containers
Warm temperature
Low, creeping, but will vine upward


Flame violet, Episcia cupreata
3 to 6 inches high
Medium light
Closed, open containers
Warm temperature
Grow as African violet


Foam flower, Tiarella cordifolia
6 to 12 inches high
Medium, bright light
Closed, open containers
Cool temperature
Woodland plant


Freckle-face, Pink polka dot, Hypoestes panguinolenta
Over 12 inches high
Bright light
Closed, open containers
Warm temperature
Pinch back to prevent legginess


Gold dust dracaena, Dracaena godseffiana
3 to 6 inches high
Medium light
Closed, open, dish containers
Warm temperature
Slow growing


Goldfish vine, Columnea microphylla
1 to 3 inches high
Medium light
Closed, open containers
Warm temperature
Trailing plant


Haworthia, Haworthia spp.
1 to 6 inches high
Medium, bright light
Dish
Warm temperature
Best for desert garden


Heart-leaved philodendron, Phildendron scandens oxycardium
Over 12 inches high
Medium light
Closed, open, dish containers
Warm temperature
Climber or trailer


Hen and chicks, Echeveria spp.
1 to 3 inches high
Bright light
Dish
Warm temperature
Best for desert garden


Hepatica, Hepatica americana
3 to 6 inches high
Medium light
Closed, open containers
Cool temperature
Woodland plant


Irish moss, Selaginella spp.
1 to 3 inches high
Low, medium light
Closed, open containers
Groundcover. Likes most organic soils


Jade plant, Crassula argentea
Over 6 inches high
Bright light
Dish
Warm temperature
Don't overwater. For desert garden


Maidenhair fern, Adiantum cuneatum
6 to 12 inches high
Medium light
Closed, open containers
Warm temperature
Dead fronds may need removal


Miniature holly, Malpighia coccigera
Over 12 inches high
Medium light
Closed, open, dish containers
Warm temperature
Avoid overwatering


Miniature peperomia, Pilea depressa
1 to 3 inches high
Medium light
Closed, open containers
Warm temperature
Avoid overwatering


Miniature sweet flag, Acorus gramineus variegatus
6 to 12 inches high
Bright light
Closed, open, dish containers
Warm temperature
Grasslike with white stripes


Miniature wandering Jew, Tahitian bridal veil, Gibasis geniculata
3 to 6 inches high
Medium light
Closed, open, dish containers
Warm temperature
Low light creeper or trailer


Moss sandwort, Arenaria verna
1 to 3 inches high
Bright light
Open, dish containers
Cool temperature
Needs excellent drainage


Neanthe bella palm, Chamaedorea elegans 'bella'
Over 12 inches high
Medium light
Closed, open, dish containers
Warm temperature
Slow growing


Nerve plant, Fittonia spp.
3 to 6 inches high
Medium light
Closed, open containers
Warm temperature
Leaf veins white or pink


Oxalis, Oxalis spp.
3 to 6 inches high
Bright light
Closed, open containers
Cool temperature
Cloverlike foliage


Panda plant, Kalanchoe tomentosa
3 to 6 inches high
Bright light
Dish
Warm temperature
Suitable for desert garden


Parrot leaf, Joseph's coat, Alternanthera spp.
Over 12 inches high
Bright light
Closed, open, dish containers
Warm temperature
May be kept compact by pruning


Partridge berry, Michella repens
1 to 3 inches high
Medium light
Closed, open containers
Cool temperature
Groundcover


Piggy-back plant, Tolmiea menziesii
3 to 6 inches high
Medium light
Open, dish containers
Warm temperature
Small plants grow on old leaves


Pigmy cactus, Rebutia spp.
1 to 3 inches high
Bright light
Open, dish containers
Warm temperature
For desert garden


Pipsissewa, Chimaphila umbellata
1 to 3 inches high
Medium light
Closed containers
Cool temperature
Woodland plant


Podocarpus, Podocarpus macrophylla
Over 12 inches high
Medium light
Closed, open, dish containers
Warm temperature
Slow growing


Prayer plant, Rabbit's tracks, Maranta spp.
6 to 12 inches high
Medium light
Closed, open containers
Warm temperature
Leaves fold together at night


Rattlesnake plantain, Goodyear pubescens
1 to 3 inches high
Medium light
Closed containers
Cool temperature
Woodland orchid


Red bird, Devil's backbone, Pedilanthus tithymalaoides
Over 12 inches high
Medium, bright light
Closed, open, dish containers
Warm temperature
Foliage variegated


Rosary vine, String of hearts, Ceropegia woodii
1 to 3 inches high
Medium, bright light
Open, dish containers
Warm temperature
Low light trailing vine


Sander's dracaena, Dracaena sanderiana
Over 12 inches high
Medium light
Closed, open, dish containers
Warm temperature
Cornlike plant with white stripes


Satin pellionia, Pellionia pulchra
1 to 3 inches high
Medium, bright light
Closed, open containers
Warm temperature
Creeping vine


Spider Aralia, Dizygotheca elegantissima
Over 12 inches high
Medium, bright light
Closed, open, dish containers
Warm temperature
Needs pruning to keep low


Spider plant, Airplane plant, Chlorophytum comosum 'Vittatum'
3 to 6 inches high
Low, medium light
Closed, open, dish containers
Warm temperature
Forms new plants on runners


Spotted wintergreen, Chimaphila maculata
1 to 3 inches high
Medium light
Closed containers
Cool temperature
Woodland plant


Strawberry begonia, Saxifraga sarmentosa
1 to 3 inches high
Medium light
Closed, open, dish containers
Warm temperature
Runners like strawberry


Stonecrop, Sedum spp.
1 to 3 inches high
Bright light
Dish container
Warm temperature
For desert garden


Sultana, impatiens, Impatiens walleriana
Over 12 inches high
Medium, bright light
Closed, open, dish containers
Cool temperature
Needs pruning to keep low


Sundew, Drosera spp.
1 to 3 inches high
Bright light
Closed containers
Warm temperature, insectivorous plant


Swedish ivy, Plectranthes australis
1 to 3 inches high
Low, medium light
Closed, open, dish containers
Warm temperature
Low, creeping, very durable


Sweet olive, False holly, Osmanthus heterophyllus
Over 12 inches high
Bright light
Open containers
Cool temperature
Hollylike leaf, may need pruning


Table fern, Victoria fern, Pteris spp.
6 to 12 inches high
Medium light
Closed, open containers
Cool temperature
Tropical fern


Variegated ovalleaf peperomia, Peperomia obtusifolia variegata
3 to 6 inches high
Medium light
Closed, open containers
Warm temperature
Colorful foliage


Venus fly trap, Dionaea muscipula
1 to 3 inches high
Bright light
Closed, open containers
Warm temperature
Insectivorous plant


Waffle plant, Hemigraphis 'Exotica'
Over 12 inches high
Medium, bright light
Closed, open containers
Warm temperature
Purplish leaves


Watermelon peperomia, Peperomia sandersii
3 to 6 inches high
Medium, bright light
Closed, open, dish containers
Warm temperature
Avoid overwatering


Wintergreen, Gaultheria procumbens
1 to 3 inches high
Medium light
Closed, open containers
Cool temperature
Woodland plant
 
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#2 ·
I found this post to be extremly informative... copying to my desktop in a new notepad file for future reff... Thanks!
 
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