In Terrariums
​Using aquatic plants in terrariums is a lot simpler than using them in aquariums. I believe that this is due to the fact that all of the complexities that need to be considered under water don't exist in terrariums.
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In my experience the only thing that is required is water. I’ve placed plants in a jar part filled with water on many occasions. This works because the plants will actively root in and feed from the water and still have a moist atmosphere within the jar to grow into.
With this information, you can be rather free with the materials you use to construct an emergent terrarium. If you use an absorbent material like leca or sphagnum moss, it will hold a lot of liquid and feed the humidity needed for above water growth. If you use less absorbent materials then you can create a reservoir or false bottom to hold the moisture needed to humidify the atmosphere. Of course to modulate the amount of nutrients present in the terrarium you can add more or less soil to the substrate or leave soil out of areas that you'd like to be clear of plant life.
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When it comes to plant selection, you must remember that not all aquatic plants will grow out of water. Most root feeding plants, grasses and rosettes (I have found) don’t do well above water. The plants that have been the most successful for growing in terrariums are stem plants; even so, some are more delicate than others and will require more patience and attention or they will just not grow.
This is where research and experimentation will come into play.
In most cases you can search ‘*plant name* grown emersed’ in google images and get a good idea of whether it can be or has been grown out of water by others. If not it can never hurt to take a cutting and try growing it in a terrarium yourself.
I’ve had plenty of unexpected success growing plants like Cryptocoryne balansae (rosette) out of water, so I never write any plant off as impossible.
Once you get the hang of growing a good roster of aquatic plants out of water you now have a new set of colours on the palette with which you can create beauty within a terrarium and greater possibilities in terms of the environments you can form; mini paludariums would be a great example of this greater creative bandwidth.
