A closed terrarium with orchids is possible but won't be easy. They need a lot of attention and care which you can't provide in a closed terrarium (without opening the container). On one hand, they need a lot of water and on the other hand their petals may not get wet. This'll be hard to accomplish due to the condensation inside your closed terrarium which you can't prevent. I'll tell you how you can try to keep an orchid inside a closed terrarium regardless.
Tip! If you need a substrate for your orchids, read this review.
What are orchids?
Orchids are flowers and biologically belong to the flowering plants. Flowering plants are characterized by protecting their seeds with petals. The special type of petal is called a carpel and is the female reproductive organ of flowers. The blossom is one of the most remarkable features of orchids and is seen s especially beautiful. Because of that, orchids are also called queens of flowers.
There are over 1000 genera of orchids with about 28.000 species. If you count hybrids as well, there are over 100.000! All orchids are characterized by their grown together pollen grains called pollinia. Some need symbiotic mushrooms to help with pollination. This however isn't problematic for closed terrariums as a single orchid can grow indefinitely. A maximum lifespan is currently unknown.
Orchids in a closed terrarium
Orchids appear in three kinds of growth, or rather on three kinds of growth mediums. All three of them are suitable for closed terrariums. They are the following.
- epiphytic form (ontop of other plants)
- terrestrial form (on soil)
- lithophytic form (ontop of stones)
Epiphytic orchids sit ontop of other living plants. In the tropical rainforest they're often found sitting in tree canopies and don't need any substrate like other plants would. More than half of all orchids are epiphytic. They are notorious for they thick roots that need a lot of oxygen and water. They take their nutrients from the tree they're sitting on or directly out of the air.
Caring for an orchid is not that easy. Let's begin with the substrate. If your using normal potting soil, your orchid will wilt quickly as it doesn't get enough oxygen. Instead, you'll need something more coarse. Raw puffed clay balls are quite good here. The gaps are large enough for enough ventilation. Puffed clay balls are also beneficial since they soak up water and prevent the orchid from sitting in standing water. Standing water causes signifikant damage to their roots. You can see that an orchid needs water by looking at its roots. If their white, they're too dry. You're good if they're a dark green color.
Orchids need a lot of light but hate direct sunlight. In the tropical rainforest at the equator they get a very constant amount of light of about 12 hours per day. In the northern hemisphere this amount can vary between 2 and 16 hours of sunlight per day. Thus, you'll need special grow lights in winter. Learn more about plant lighting here.
Humidity will be a bit more complicated. Orchids really like high humidity which you can easily accomplish in a closed terrarium. But they really water drops on their beautiful petals. This will be difficult to prevent because of the daily water cycle and the corresponding condensation. You'll have to try out how long an orchid can stay dry enough in a closed terrarium.
When putting an orchid into a closed terrarium you should first cleanly cut off all old roots and leaves and then water it with lyme-free water. You're best to take distilled water or rain water. Tap water often contains a lot of lyme. An example for epiphytic orchids is the phalaenopsis.
Like most plants, terrestrial orchids grow in normal soil. Their roots are thinner and not quite as delicate as the epiphytic variant. However, they need quite loose substrate to anchor in, which you can mix yourself. For that I already wrote a guide on how to mix a substrate. For very loose substrates with akadama and lava granules you can find more details in the article about bonsais. The looser the soil the better the ventilation and okxygen intake of the plants. Just like the epiphytic variant, terrestrial orchids need a lot of light but can't take direct sunlight. So don't put it right on the window sill, if you can.
Since they originate in the rainforest they like it warm. Your room temperature of 20°C is a good baseline. Due to the greenhouse effect your closed terrarium will always be a little warmer anyway. Orchids love temperatures between 20°C and 30°C. So you really don't need to worry about that. You can easily put them over a heater without them caring. However, at night you should put it next to an open window if the temperatures drop below 15°C.
In winter your orchid would like to keep its 20°C to 30°C and would love to be illuminated as well. You can use grow lights here and keep your closed terrarium with orchid over a heating element. An example for terrestrial orchids are Cymbidium.
The lithophytic variant of orchids is especially interesting. Lithophytic orchids directly grow on stones and in same cases can even dissolve the stone to put their roots inside. They get their nutrients from the stones themselves, nearby moss and from the air. Keeping lithophytic orchids isn't really different to epiphytic orchids. You can choose these quite as well.
Are there blue orchids?
Well, not really. In an earlier version of this article I thought that orchids came in all colors of the rainbow, but sadly this isn't true. A nice user on Facebook pointed out my mistake.
Really blue orchids can only be made by coloring other colored orchids. How exactly this works is explained in this article by Amanda Matthews. The color isn't permanent. So you can't keep a closed terrarium with a blue orchid forever. Nature itself comes closest to blue orchids with vanda orchids. They however are rather purple than blue.
Would you rather like carnivorous plants or bonsais?
A closed terrarium with orchids is definitely possible but not that easy. The temperature and humidity shouldn't be a problem for your plant. 20°C to 30°C are optimal in any case, no matter the orchid. Watering it can be critical. Your orchid needs a lit of water, but may never sit in standing water. Its blossom may also not get wet. In winter, orchids don't get enough sunlight per day which is why you need to help your closed terrarium out with special grow lights.
If you need some ideas for bottle gardens with orchids, check out this article here.