Nathaniel Ward was an Englishman who loved to observe the behavior of insects and was fond of enclosing them in glass jars. Once, he forgot about one of his jars and, when he noticed it again, a fern had begun to grow in it. Somehow, unawares, a spore from a fern had found its way into the jar before it was sealed. This event occurred in 1842 and when word got out about it, Victorian England became obsessed with growing plants enclosed in glass, dubbing the container in question a “Wardian case.”
Ward began to construct elaborate glass boxes to contain his plants. Protected on all sides by clear glass panels, he shipped plants to Australia where, after several months, they arrived in prime condition. By return ship, his boxes were filled with tropical Australian plants which arrived in London also without blemish.
The idea that plants could thrive in sealed glass containers without ventilation was an astonishing discovery. We have since learned that plants do require oxygen at the cellular level. However, this essential oxygen is produced by plants themselves as a byproduct of photosynthesis.
(As you probably know, if it were not for plants, we could not breathe since atmospheric oxygen is produced entirely by plants. However, as you may not know, the vast majority of that oxygen comes from unicellular oceanic organisms known as phytoplankton. Although microscopic, these organisms, during what is known as ocean bloom, combine together to form layers of green or turquoise slime that may cover hundreds of square miles. Although each phytoplankton lives for only a few days, long-lasting blooms of these rapidly replicating micro-organisms will endure for several months at a time.)
Today, those glassy Wardian cases are known as terraria (plural of terrarium). A terrarium may be open or closed, depending on the species being grown. Closed terraria are meant for tropical species such as orchids, ferns, tillandsias, and mosses. The moisture inside is recirculated, condensing on the roof and sides of the terrarium, falling down in droplets, and then condensing again, keeping the humidity, upon which tropicals depend, at a high level. Still, you will want to remove the top of your terrarium once a week to allow excess moisture to escape since continually wet surfaces could lead to moldy growth. By the same token, lack of condensation or wilted plants are a sign that you need to add water to the soil.
Ideally, the soil itself should be sterile, consisting of peat moss, perlite, and vermiculite, in order to minimize the possibility of growth on the part of pathogenic fungi or bacteria. An open terrarium, on the other hand, provides an excellent microclimate for succulents and cacti, where excess moisture cannot accumulate.
A terrarium is but one example of a vivarium, the generic term for a containerized mini-ecosystem in which plants, animals, or a combination of them can grow. Under the vivarium rubric, you will find aquarium, riparium, and paludarium.
While an aquarium is favored by fish lovers, a variety of plants can grow in them, too, providing a source of oxygen for the fish. The problem here is that plants that grow submerged in water have uniformly green foliage, making their visual presence rather predictable.
A riparium, on the other hand, mimics conditions on the edge of a lake, pond, or stream. A riparium is a watery abode for fish and submerged plants, but land plants whose roots are unphased by constant moisture grow there, too. Colorful plants such as Coleus and Alternantheras that root easily in water grow in a riparium as long as their foliage can be supported so it remains above water. You can even bring in a water lily or two, and the foliage of many indoor plants — such as pothos, arrowhead plant (Syngonium), and spiderwort (Tradescantia) — will flourish when their roots are bathed in water.
Tip of the Week: A paludarium (palus = swamp, arium = enclosed container) is the most challenging but potentially rewarding environment for the indoor naturalist. You will still have an aqueous bottom for your fish but the water will also be a place where turtles and frogs can play. There will be rocks and pieces of driftwood sticking up above the water on which the turtles and frogs can sun themselves and upon which the sort of riparium plants mentioned above would also find support. Elaborate paludaria keepers do not stop at fish and amphibians, but may even add a bird or two to complete a trifecta menagerie where water, land, and air serve as the habitat for creatures appropriate to each, complimented by colorful swamp-loving and tropical flora of all kinds.