Open terrariums - the type we sell in our retail studio and online, and the most common and easy to care for. These are glass vessels with an opening that allows air circulation and through which you'll care for your plants. We're going to detail care for open terrariums.
HOW TO CARE FOR A TERRARIUM WITH SUCCULENTS
Succulents - plants with thick, fleshy foliage and stems that store water, are by far the most common plants seen in terrariums. This makes a lot of sense, because succulents are typically comfortable not receiving too much water, and don't need much root space to thrive, making them perfect for small enclosures. Plus, many species stay small and compact, allowing them to live for years in a terrarium without transplanting.
Here's how to care for this type of terrarium:
Light: Save for some lower-light tolerant species like Haworthia and Gasteria, most succulents prefer bright, if not direct, light. Place your succulent terrarium in a very bright and warm spot, keeping in mind that glass tends to magnify direct sun, and can potentially burn your plants.
Water: Succulents are drought tolerant plants, and are highly susceptible to root-rot. Combined with the fact that terrariums do not have drainage holes, you'll want to water your succulent terrarium very sparingly, when the soil has gone almost completely dry. Water sparingly around the base of each plant using a watering can or a spray bottle. Most succulents will tell you when it's time to water by puckering slightly in their leaves. This is a great indicator for when it's time to water your terrarium
Troubleshooting: Shriveled leaves? Time to water. Mushy, brown or black leaves? You're watering too much. Remove these plants and replace with comparable specimens, taking care not to water quite as much. Reduce watering during winter.
HOW TO CARE FOR A TERRARIUM WITH CACTI
All cacti are succulents, but not all succulents are cacti. The cacti that most folks are familiar with come from the desert. For a terrarium with cacti, you can follow identical instructions for your succulent terrarium, detailed above, with a few adjustments:
Cacti tend to be even more susceptible to rot than succulents. Take extra care not to over-water.
Cacti need very bright light to thrive. They should be fine to receive direct light.
As always, there are exceptions to the above rules. "Jungle cacti" like Rhipsalis, Hatiora and Epiphyllum, will not like bright light, and prefer more water than most cacti.