Indoor Gardens

A Guide To Tackling A Terrarium

by Tina Mast // January - February - March 2023

Terrariums require little in the way of watering or feeding and are a fun way to enjoy plants indoors – especially during the winter months when we may not be able to enjoy our outdoors gardens as much as we do the rest of the year. They can be either enclosed containers such as apothecary jars or aquariums, or open-ended containers such as brandy snifters or fishbowls. Enclosed containers are most practical for growing small plants that like humid conditions. Open containers will require more watering than enclosed ones and are better suited for succulents, cacti, and other plants that prefer less humidity.

Before planting your terrarium, select your plants by experimenting with different combinations of small ones and by choosing those that will do well in the light in which they will be placed. South and west facing windows provide strong, bright light. East facing windows provide medium light. North-facing windows and fluorescent office lighting is considered low to medium light. The plants should also have similar moisture needs.

Suggestions: Let most of the plants be green with not more than one variegated plant. Use plants of varying heights with taller ones in the back. Make sure plants are small enough or the container is large enough that leaves won’t touch the glass of the container. Plan where any decorative items will go in relation to the plants.


– A clear glass (or plastic) container, open or enclosed with no drainage holes
– Activated charcoal
– Pebbles, clay pellets, or sand for drainage
– African violet potting mix
– Fiberglass screen or sheet moss
– Plants
– Spray bottle of water
– Chopsticks or ¼ inch dowel rods and a cork (if terrarium is too tall and narrow to reach the soil with your hands)
– Long, slender tongs
– Large kitchen spoon
– Decorative items such as stones, shells, driftwood, fairy garden accessories, etc. (optional)
– Prepare to plant your terrarium by first cleaning the container thoroughly with soapy water and drying it, and dampen the potting mix with a few sprayings of water.


Place ½ inch layer of pebbles, clay pellets, or sand in the bottom of the container. This is the minimum, but the amount can vary. In general, about ¼ of the terrarium’s volume should be comprised of draining material (pebbles) and growing medium (potting mix).

Cut the fiberglass screen to a size that will fit over the pebbles and lay it over them. (While optional, this keeps layers separate, which helps with drainage and detoxification.)

Place ½ inch layer of activated charcoal over the fiberglass screen. Charcoal helps eliminate chemicals that could be toxic to plants and is especially important in enclosed terrariums. Place another layer of screen or sheet moss over the charcoal to keep potting mix from sifting in. The moss can also look nice as a green layer in the terrarium.

With your large spoon, scoop in dampened potting mix over the screen. Generally, a minimum depth of 1½ inches is required, but you may need more if the rootballs of your plants are deeper than that.

Add your plants. If the terrarium is narrow and tall, try using the chopsticks or dowel rods to create a hole in the potting mix before setting the plants gently in, using slender tongs. Gently tamp down the soil using your fingers, or if you can’t reach, a cork attached to a skewer or stick. Add more soil, if necessary. Spray the soil around the plants to moisten it and mist the plants to wash off any potting mix that stuck to the leaves. Mist again the following day. Add your decorative items, place your terrarium in its spot, and enjoy!

Terrarium Care

An enclosed terrarium may not need water for four to six months. If you don’t see condensation on the inside, it may be time to water. Open terrariums need water occasionally, but not as often as other houseplants. Avoid standing water in the pebbles and charcoal – better a little too dry than too wet. Let plants dry before replacing the lid on an enclosed terrarium. Trim plants periodically to keep the size down. Don’t fertilize the first year. Thereafter, apply a quarter-strength solution of houseplant fertilizer one or two times a year, as needed.

Tina Mast

Communications director at Homewood Nursery in Raleigh.