Terrarium Plants Are Too Big

Terrariums were popular during the 1960s and 1970s, and are making a comeback today.

Terrariums are a collection of plants within a glass container. Open terrariums are not sealed and have a small opening to allow air circulation and water evaporation. Closed terrariums are sealed and make their own ecosystem. Both require regular maintenance to ensure plants do not get too big and out of control.

Plant Removal

Overgrown plants in a terrarium almost always need to be removed. It is possible to leave some in and pull out those that are seriously overgrown and cannot be clipped back. If more than half the plant needs to be pruned, it is better to remove it and plant something smaller in its place.

Pruning

Pinch back the tips of plants to make them less crowded and more manageable. This encourages bushy growth instead of the plant growing too tall. Pinch or cut stems above a leaf or at the joint where branches meet. Use fingers, scissors, sharp knives or razor blades. Mount some tools on sticks with tape to get to small areas within a partially enclosed container.

Cleaning

Always remove any pruned material, never letting it sit at the bottom of the terrarium to rot. Whenever a plant shows any sign of trouble, such as yellow or dry leaves, remove it immediately. If it is diseased, quick removal may save the terrarium. Always trim leaves away from the inside glass walls so mold will not develop.

Fertilization

Overfertilization is the most common cause of overgrown plants. Avoid feeding the terrarium for the first year, using fertilizer only if plants start to look pale or yellow. Use water-soluble houseplant fertilizer at half strength and half as often. For example, if the instructions say to use 1 tsp. of fertilizer per gallon of water twice a month, substitute ½ tsp. per gallon of water and apply once a month. If plants grow too fast, cut back on the frequency of fertilizing.

References

• Oklahoma Cooperative Extension Service; Terrariums; Doug Needham, et al.
• University of Florida IFAS Extension; Terrariums; B. Tiga, et al.
• Tom's Terrariums and Glass Gardens: Caring for Your Terrarium
• Clemson Cooperative Extension; Indoor Plants -- Terrariums; Debbie Shaughnessy, et al.; September 1999
• Toronto Botanical Garden; Terrariums; 2007

Resources

• University of Kentucky Cooperative Extension Service; Making a Terrarium; Madge Balden Adams