Best Plants For Open Terrariums | Slick Garden. Terrarium plants are small, slow-growing plants that are housed in glass jars. And if you are not good at caring for houseplants, they are the ultimate shortcut to greening yourself. Terrariums can make the interior more lively and inviting. They are also quite versatile in size – you can either grow up or stay with them. They make a delightful addition to any home because they are low maintenance and can easily fit on a tabletop.