How to make an Open Terrarium

I’ve made a couple of open terrariums recently and here are some tips that might help you get started. I think it’s a lot easier to make an open terrarium (a vessel which is partially open and allows air flow) rather than a closed terrarium (which creates a micro-climate within the vessel). Closed terrariums require trickier to source items like activated charcoal to purify what can quickly become a funky environment, so I’ve kept it simple and easy with an open terrarium.

What you need to make an open terrarium:

1. A suitable glass vessel: classic terrariums can be found online but they can also be pricey. I’ve made some in jam jars and lanterns and they work just as well.
2. Some potting grit or gravel, ideally 5mm aggregates in a colour you like. I found that searching for horticultural potting grit online eventually found me a bag of what I needed. People sell kits on Etsy and Ebay but I think they are very expensive.
3. Compost with good drainage. You can buy special cacti and succulent compost but I’ve gotten by with simple peat free compost. If you have leaf mould at home then great! If you have some sand or potting grit you can mix into the compost then great too! This will all help improve drainage. Also when you buy your plants, you may notice there are white bits in the compost, this is most likely perlite, which is used as I’m sure you have now guessed, to improve drainage!
4. Plants.  An open terrarium lends itself well to plants that like a dry environment, cue your succulents and cacti. There are many different varieties, but some of my favourites are: Echeveria, Sedum, Aloes, and Crassula. This are often available in florists and garden centres but can also be bought online. Try to get very young, small plants as then you can have some different varieties on show in your terrarium.
5. Invest in a mister or clean out and reuse a household spray. It’s the easiest and best way to water your terrarium.

Tips on how to create your open terrarium:

Its obvious, but first make sure the plants you want actually fit in the vessel, and with a bit of space between them! Once you are happy with your layout, spoon in a generous layer of grit into the bottom of your vessel. Then spoon in your compost, make sure it’s deep enough to accommodate the roots of the plant you wish to put in. You can use the spoon to make a planting hole, before lowering in your plant. If the roots are way too long, don’t despair, you can trim them to fit, but remember the plant isn’t going to love it so only do it if you need to. Once in, press down gently with your fingers to help anchor the plant, and make sure the roots are safely under the compost, you can add a bit compost if needed. I normally give the plant a little mist at this point.

Start to spoon your potting grit around your plants. This has a dual function, providing a top dressing which will help your plant stay dry and prevent rotting off, it also looks nicer than compost! I do this as I go because it’s less messy than doing it all at the end once the plants are in.

Once everything is in, give it a mist and then wipe down the sides with a cloth. I added a few shells that I found on a beach to this terrarium, so if personalisation is your thing, go for it! Place your terrarium in a position that will receive ample light, but not direct sunlight, remember it’s in a glass vessel. Use your mister to give it a water, I think once a week should do it. In time your plants will likely out grow your vessel, but you can always replant it. You can help things, by removing offsets as they grow in late spring, and you can even propagate these. I’ll be back with a video to show you how to do this when the time comes.

Good luck and please get in touch with any further questions you might have, or even better photos of terrariums you’ve made yourself. I’m really enjoying mine and it’s certainly brightening up a slightly grey January.

Hannah x