- Water your plants. If your terrarium is open, water the plants occasionally. Though airtight terrariums don’t require watering, plants in open containers need to be watered about once every week or two. Succulents and cacti can be watered once a month.
- Keep your plants healthy. As soon as you notice weeds, mold, or sick plants, remove them immediately. You should also remove wilting parts of the plant, such as dead flowers.
- Let in some fresh air. If your terrarium is airtight, it is a good idea to occasionally air it out. If your plants are wilting or there is excessive condensation on the sides of the terrarium, allowing the container to air out will be beneficial.