Well I grow alot of Hoyas in Terrariums. and I also grow the Ric Rac cactus but I've never thought about putting it in the terrarium. I guess it may enjoy it. I grow mine in their individual pots and use the terrarium more for humidity. So I think I would probably try Ric Rac the same way. Maybe put it in a fast draining mix (lots of perilite) and set pot and all in terrarium. Watch it closely....?

Here is a picture of mine. It has not bloomed yet. I've had it 1 year.

I wouldn't recommend it -- especially not in closed jars like you have pictured. Very few plants do well for any real length of time in humid stagnant air (fungal and bacterial issues tend to abound). And if the plant does manage to thrive under such conditions, then there is the eventual issue of what to do when it outgrows that container? Though you might be able to find a much larger jar for the next period of its life, sooner or later -- with a plant that gets as big as those do -- you are left with needing to plant it in "normal" conditions (a pot or basket). Then the plant goes through the trauma of attempting to adjust from constant 90-100% humidity to the far lower RH levels in your home or outside. Many plants die during such a drastic transition.

Now if you are thinking of a large terrarium which will also have good air circulation, then you will have a much better chance of success. Considering how big those devils get, though, I'm not sure how long one would fit even in a large terr. (And not being "viney" like a Hoya, you won't be able to just coil it around.)

Hi! Thanks for the input. I forgot I had posted this question. :-)