Chapter 15 - Terrariums

In the first chapter of this book, we mentioned the use of terrariums as one of the methods of displaying house plants sometimes with extremely fascinating effects. This is a very specialized part of home gardening, but an extremely interesting one. A great many woodland plants which prosper in their natural environments fail to grow at all in the house due to the lack of moisture in the air. In nature, these plants live in an atmosphere in which the humidity is generally greater than 75 % an atmosphere which if transferred indoors would quickly rot every piece of upholstered furniture you own, to say nothing of ruining the finish on all the woodwork. Terrariums provide this humid atmosphere and allow you to bring the forest plants home.

The basic theory behind the terrarium is that in a closed container the moisture which the plants take up through their roots and transpire through their leaves is condensed and eventually returns to the soil again, keeping the plants watered and at the same time keeping the air within the container at a point just below saturation. Theoretically, if you had a container which was sealed airtight, the process could be continued over and over ad infinitum with never a drop of water added. Obviously, this is impossible, but even if it were possible it would be undesirable, as in an airtight case, the tendency would be for the sides to cloud up with moisture, thus obstructing the view of the inside. The ideal is a case that can be ventilated from time to time, as discussed below.

Containers to use. Terrariums are sold commercially in all sorts of shapes, sizes and forms. You can buy them already planted in tiny cocktail glasses or large bottles, in fishbowls and decorative jars. These are all perfectly good and usable containers the only disadvantage being that they are usually over planted for effect, especially the smaller ones, and will quickly become overcrowded as the plants begin to grow.

If you are thinking of starting your own terrarium at home, you will probably find that you have all the material and equipment you need around the house. Fish tanks, especially those that are not too big and unwieldy, make very good terrariums. All you need for them is a glass top. If you are going to start from scratch, you can build your own container using a flat, low-sided box for the bottom, and fitting it with glass sides which can be taped together, and a glass top. The only problem with these homemade arrangements is that unless you are a more expert craftsman than most the result is pretty fragile and will not stand to be moved. Small fish tanks can be bought for very little money and are generally quite sturdy.

Although the theoretical airtight terrarium would have no openings whatever, it is safer to provide the container with several drainage holes so that you avoid the risk of over watering and rotting the roots of your plants. If you use a large brandy glass or some other container for which drainage holes cannot be provided, then you must be extra careful that there is a good layer of drainage material (pebbles, gravel, crocking, etc.) at the bottom, and that the soil is sweetened with a sprinkling of charcoal.

Laying the groundwork. The way you place the soil at the bottom of the terrarium is extremely important. As we have just said, it should always be well drained. Start out by placing large pieces of concave crocking over each of the drainage holes to prevent the soil from leaking out. Then add an inch or so of good drainage material. Follow this with another layer of a couple of inches of a good potting mixture, such as those that can be bought in a garden-supply store. It should be filled in firmly, but not tamped down too tight. The soil should be slightly damp, but not soaking wet. Then place the plants, which should be ready nearby, by digging small holes large enough to accommodate their balls of earth in a pleasing arrangement. It is a good idea to work out the arrangement ahead of time so that you know in advance just where you want each plant to grow.

Watering, ventilation and sun. When your plants are all in position, the soil should be well watered. If you can do this in the kitchen sink or in the bathtub where you can give it a thorough wetting and then allow the excess to drain out, so much the better.

The frequency with which terrariums must be watered after they have been started depends on how much ventilation they are given. Although opinions vary, it has been our experience that the plants will prosper if they are kept covered during the day and the top is partially slid off at night. If this system is followed, we think you will find that your terrarium garden will need watering only once every few months.

Terrarium plants need sunlight, but in limited amounts. An east or west window will do the trick, or a south-facing location, if there is a glass curtain between the window and the container.

Plants to grow. In addition to lichens and mosses, a good many plants which grow in the open air of your living room will prosper as well in miniature form in the ter-rarium. Below is a partial listing. Your florist or nursery supplier can give you many other suggestions.

botanical name                          popular name
Adiantum cuneatum                  Maidenhair Fern
Asparagus plumosus                 Asparagus Fern
Begonia imperialis                     Begonia Dumb Cane
Dieffenbachia Dracaena            Gold Dust Plant
godseffiana Maranta                 Arrowroot Sword
variegata Nephrolepis               Fern Watermelon
Peperomia sandersi                   Begonia
Philodendron cordatum             Philodendron
Saintpaulia ionantha                  African Violet
Zebrina pendula                        Wandering Jew

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