A terrarium puts a rain forest in the palm of your hand

The first terrarium was invented quite by accident. In 1830, an amateur naturalist in London placed a moth chrysalis in a sealed glass jar to await its metamorphosis. Months later, he noticed a tiny fern had sprouted inside the jar.

History does not record what happened to the moth, but Nathaniel Ward's terrarium was an instant hit. Soon, elaborate glass enclosures - called Wardian cases - were cropping up in fashionable Victorian parlors.

Aside from their trendiness, such glass cases were a boon to science. Botanists could now ship plant specimens from as far as Australia and, sealed in their airtight containers, such plants could survive everything from equatorial heat to the chill of an English winter.

The concept is simple: Plants inside the covered glass container give off moisture, which condenses, trickles down the glass and back into the soil. The terrarium, if made with the right type of soil and filled with compatible, moisture-loving plants, becomes its own miniature ecosystem and needs little maintenance.

Here's how to build your own tiny landscape:

*Start with a clean, clear-glass container (colored glass doesn't allow enough light in). A wide opening is helpful for reaching inside to install plants. Find or make a lid to fit on top. (Glass is best as it allows in more light, and, unlike metal, won't corrode.

*On the bottom of the container, spread a layer of pebbles about 1/2-inch deep. These allow excess water to drain away from plant roots. Next, add a thin layer of ground charcoal (which provides drainage, sweetens the soil, and absorbs impurities). Then add sterile potting soil to about 2 or 3 inches deep.

*Plan how your design will look before you start adding plants. Remember that scale is everything. Taller plants are best in the center or back, with shorter ones grouped in front. Go for contrasting textures - a serrated-edge fern next to a velvety moss, or round, broad leaves next to a finely cut ivy.

*Make an indentation in the soil for each plant. Unpot it and gently shake off as much soil as possible. Trimming the roots will also make it easier to install and encourage root growth. Settle the plant in, firming the soil around it. Don't overcrowd.

*Depending on the look you're trying to create, you can accessorize your terrarium with miniature props. If you're going for a natural approach, you can add moss, stones, and twigs. If a Lilliputian landscape is what you're after, add tiny china animals, doll furniture, or small ceramic houses.

*Water sparingly when first planted, and thereafter only when soil feels dry. To avoid disturbing the soil or wetting leaves, pour water slowly over a rock or use a funnel and plastic tube. As there is no drainage in a sealed terrarium, overwatering is the most common mistake, causing leaves to yellow and stems to rot. Check condensation on the sides of container. Moisture on half the container or less is good. If there's too much, open the lid or wipe the sides down.

*Place the terrarium in a spot with diffused light, not direct sunlight - which can raise the temperature inside and scorch plants. Keep away from heat sources such as radiators.

*Pinch plants back or replace them when they become too large.

*Fertilizer isn't recommended.

Follow these steps and you'll be rewarded with a fascinating ecosystem that practically looks after itself.

Good plant choices for terrariums

Tall

Acorus

Artillery plant

Arrowhead vine

Aucuba

Australian laurel

Dracaena

Maidenhair fern

Parlor palm

Podocarpus

Plumosa fern

Snake plant

Zebra plant

Medium height

Aluminum plant

Asparagus fern

Begonia

Boxwood

Brake fern

Chinese evergreen

Ferns

Violets

Pellionia

Peperomia

Prayer plant

Venus flytrap

Low

Creeping Charlie

Baby's tears

Button fern

Creeping fig

English ivy

Irish moss

Miniature slipper plant

Nerve plant

Scotch moss

Strawberry begonai

Source: Lexington Gardens, Lexington, Mass.

(c) Copyright 2000. The Christian Science Publishing Society