Which plants? • Plants in small, 3cm-6cm wide pots What Terrariums are a fun and attractive way of growing houseplants. Choose a fully or partially enclosed type, like this, for moisture-loving plants and a completely open one for succulents and air plants. 1 Use a free-draining compost, mixed 50/50 with grit for drainage. Add even more grit for succulents. You can also add activated charcoal to help stop water turning stagnant inside. 2 Make a hole in the compost, ease a plant out of its pot and pop it into the hole, drawing the compost around the sides of the rootball. Repeat with your other plants. The plants are likely to need a new home after about a year.