Creating a Terrarium-Part 1

By Melanie Mathieson
Gardening Guru

A terrarium is a mini indoor garden in a glass container and in the 1970’s, terrariums were all the rage. After this trend died, for many years it was difficult to buy decorative glass containers suitable for planting terrariums but recently, terrariums have been reintroduced and become a current trend so supplies are available once again.
Terrariums can be planted in open or closed glass containers. A true terrarium is enclosed and therefore self-sustaining with moisture once initially watered. An open glass container will require more care and watering than a closed-container terrarium but are just as fun to grow.
Terrariums are perfect for people who don’t have the time to care for a garden or just don’t have a “green thumb” because when inside the glass, the plants require low maintenance. Terrariums are often used as decorative items because you can use a wide variety of plants and then place on desks, night tables, and other places where you wouldn’t normally place a plant or where space is limited.
The first step is to decide on either which plants you want to use or your container. Whichever you choose first, it will set the limitations for the choosing the other.
Tips for picking plants:
•Nearly any low maintenance plant can be used for a great terrarium. Choose several that have like characteristics and that will grow well together. Classic plants for a terrarium include, but are not limited to, tropical plants, ferns, mosses, succulents and cacti.
•Pick a plant that will stay small and won’t quickly outgrow the terrarium container they are placed in.
•Plants that prefer lower light or indirect light are best. Because glass can magnify light, plants kept inside a terrarium have to be kept away from direct sunlight as it will overheat the terrarium and burn the plants.
•Humidity levels in enclosed terrariums rise quickly, so plants that tolerate higher humidity are best such as succulent, tropical or woodland plants. If planning a cacti terrarium choose all cacti as you will have to make the growing conditions much drier than a regular terrarium.
Tips for picking containers:
•The container needs to be glass and deep and large enough to accommodate enough soil to accompany the plants’ roots. The container you use can be as simple as an old fish bowl or one specially made for growing.
•The container can have a lid or an open top. Here are some suggestions for types of glass containers to look for:
•Bell jars or apothecary jars are a pretty option for a taller terrarium.
•Aquariums or goldfish bowls work well as terrariums and can be left open or fitted with a piece of glass. Large aquariums can be made into terrarium tables.
•Any large glass vase or tureen. Home decorating stores are a good source. Most styles will be open on the top.
•Cloches are bell-shaped glass domes and can be placed over any planter to create an instant terrarium. Cloches are good if you want to use a decorative pot to create the base of the terrarium. Note: cloches create high levels of humidity so it will need to be raised occasionally to give plants inside a breath of fresh air.
•Miniature green houses are available in both closed and non-airtight styles. These have become popular in recent years for home decorating. Again this is often an option where you choose your own base container, place it in the tray and then cover with the glass house to create a terrarium. I have one of these that I like to grow cacti in because when placed in direct sun it gets really hot inside.
•Large glass bottles such as demi-Johns can be used but require some finagling to plant. More in the next column on that.
To plant your terrarium you will need:
•Potting Soil - choose a sterilized premixed potting soil, with sphagnum/peat moss included. You will also need to purchase perlite and some sand. If planting cacti you will need a mixture of 50% sand to 50% potting soil.
•Pebbles or gravel - are used for drainage when placed at the bottom of the terrarium and as a decorative element when placed on top of the soil. Choose stones 2.5 centimetres or smaller for drainage, but you can choose whatever you’d like for topdressing. You can get really creative here because you will see the rocks. If using rocks selected from nature make sure you have washed them in a bleach solution and rinsed well before inserting into your terrarium.
•Activated charcoal - this is a crucial component of keeping your terrarium healthy as it keeps the water from going stagnant. Recently, I have only been able to find activated charcoal at tropical fish supply stores. Note: it is not needed if you are using a container that completely drains after each watering.
•Sheet moss - is useful for lining the bottom of the terrarium as the first layer, as it provides a helpful “sponge” for mopping up excess water. I recommend this for the larger containers as smaller glass bowls will not have enough space for this layer. You can also top the exposed soil with sheet moss to help maintain moisture and give the soil a finished look.
•Decoration - pick whatever you’d like to add to your terrarium, as long as it won’t be damaged by exposure to water. Examples include miniature garden gnomes, shells, rocks, small statues, aquarium decor, or small china figurines.
This a two-part column, with the second part covering the planting techniques and general care of your terrarium. So collect your supplies so you are ready to plant when part two is published.