I bought a few hanging jars with round openings and sold them with planted succulents at a spring craft fair last year. If I had known what I know now, I would have never sold them, and I say with some dread that every single one of them sold out. I’m certain the plant life in those glass containers couldn’t handle the high-water absorption you get in a partially enclosed glass container – my only consolation is that I had marked them down to cost as I wasn’t planning on offering them again.
So let’s examine what’s at play here, because the internet sure wants us to believe that succulents in glass terrariums are a great idea. The first issue is the container choice. Any plant in glass is going to be sitting in moist soil for a L-O-N-G time. Unlike terra cotta or cement containers, the container material itself is doing nothing to wick away the moisture you’re adding to the soil. Glass doesn’t offer a lot of area for water to evaporate except for out the opening. Second, succulents are susceptible to root rot, and that can happen quickly. Ideally you want the soil to fully dry out in a few days. In my experience, it takes much longer than that for potting soil in glass to dry.
It pains me slightly to see the thousands of photos on Pinterest of succulents stuffed into Mason jars, because I’m pretty sure a follow up photo a few months later would show a slightly less beautiful picture. That said, I personally like the look of glass, and I can’t pass up a pretty jar to save my life, so here’s how to do it so your plants have a chance:
For succulents and cactus, use pumice or a super gritty soil mixture. Basically, stay way from typical potting mix. It just holds on to too much water. Bonsai Jack carries both pumice and a great succulent mix. The nice thing is you can simply pour out any excess water. I would use these options for terrariums or jars. Just a note – if using a clear jar or container, you may see roots or even algae as the plant grows. A painted glass jar will hide this, but know that even with a rocky mix, the soil will be remain moist pretty much constantly, just not soggy wet like with traditional soil in glass.
Air plants are great for terrariums! They look awesome in little beach scenes, in particular. You will need to be able to take out the plants for a weekly soaking, but that’s it for maintenance. And if you’re just using air plants, no need for soil – you can do that cool layered sand look or colored moss instead!
If you have your heart set on a traditional terrarium, there are a lot of humidity-loving plants out there that will do just fine in a glass home. Most garden centers now carry fairy garden plants, which are miniature versions of various ferns and foliage plants and suitable for terrariums. Like anything else, with practice and trial and error, you’ll figure out what works for you and the little eco-system in your home!