“Always make sure the plants are compatible and that you have the proper soil for the job,” Stone says. He recommends three options of plants for your terrarium: ferns and small plants, succulents and cacti, and air plants. Since these three vary when it comes to soil type, maintenance, and even vessel choice, you won’t want to combine these together. “Only use plants with similar watering and light requirements in the same terrarium,” he says.
Ferns and small exotic plants do well in closed terrariums since it’s easier to control the humidity and temperature—you’ll want to water these often. Air plants, on the other hand, don’t require soil and need a light spray of water once a week or a good 10-minute soaking. You don’t want to keep these in a closed container since they absorb moisture from the air—they are called air plants, after all. Lastly, succulents and cacti are great to pair together since they both require very little water. You should place them in open containers since they need to dry out between watering times.