4 ft x 3 ft x 16” cool growing terrarium in so cal, the impossible?

[Jmbaum]

We all want what we can’t have.

So after seeing all the trials and tribulations from other attempts on other orchid forums, dart frog keepers, and nepanthes growers… I’ve decided YES… I will build a large cool growing terrarium for a sunny room in Southern California.

No compression refrigeration nor Peltier coolers either, just passive circulation, age old evaporative cooling and heat sinks. Engineers and AC specialist please chime in.

I stumbled upon a deal of 50”x 36” x 16” custom reptile enclosure from a neighbor that is moving.

Aiming at keeping a plethora of Lepanthes and wide assortment of other species primarily from neotropical cloud forest in SE Ecuador.

It was a beast to move, but safely managed to get in and started sanitizing and cleaning it yesterday. Likely will need to patch up some silicone and figure out how to get the buildup on glass clean. I’ve tried vinegar and CLR so far.

Toying around with ideas on how to handle the back wall as the main growing surface. Grodan sheets on some support structure maybe? Need help with this aspect. I want to keep the plants on mounts… But also would like to closer approximate nature… not really into those sterile grid wall systems for myself. Who has experience and/or photos on that end?

So I’ll continue to update here, your thoughts and wisdom is appreciated greatly.

[SADE2020]

Very nice.. now is when your hobby take over your life hahahah, naah just kidding. But, I am curious of how is this going to be cold/cooler without help considering your climate?. And when you say sunny room, meaning you plan not to use lights either?

About the back wall that should look natural with individual mount, you are probably asking for the infamous Coke recipe. I personally don't like the egg crate walls either, I covered my tank with foam, hygrolon and cork (peat-free among all), but each plant need to be mount within the tank back wall setup and sometimes the space is not use well enough.

There are pretty nice projects in the terrarium threads, maybe a mix and match ideas. At the end you can plan all you want but when you start working is when the ideas and possibilities "flow".

Good luck,

[harpspiel]

Keep in mind that evaporative cooling only works in low humidity environments, so it will work best if you’re pulling low humidity air from outside the enclosure through a wet pad into the tank. Assuming the air outside the enclosure is dry enough.

Also, I’ve had some success growing intermediate plants in warmish conditions, I think due to a good night temperature drop. My cuthbertsonii seems ok with days that can hit 90 if it drops to mid-70s every night. This is easy for me at a mile high, but you might also be able to get there with a combination of lights off, evaporative cooling and an open window...

The only thing I do not recommend is relying on sunlight, even a little direct sunlight can cook a tank really fast, and indirect light through glass would only work for pretty low light plants.

[Jmbaum]

Originally Posted by SADE2020

Very nice.. now is when your hobby take over your life hahahah, naah just kidding. But, I am curious of how is this going to be cold/cooler without help considering your climate?. And when you say sunny room, meaning you plan not to use lights either?

About the back wall that should look natural with individual mount, you are probably asking for the infamous Coke recipe. I personally don't like the egg crate walls either, I covered my tank with foam, hygrolon and cork (peat-free among all), but each plant need to be mount within the tank back wall setup and sometimes the space is not use well enough.

There are pretty nice projects in the terrarium threads, maybe a mix and match ideas. At the end you can plan all you want but when you start working is when the ideas and possibilities "flow".

Good luck,

Definitely a big scale up. Even though it it is a fairly bright rook with east and south facing windows, I’ll definitely be supplementing the light. The tank will be positioned to not have direct light hitting it.

After thinking about it today, I’m probably going to hang rock wool germination mats off the back wall and add extra support with heavy duty suction cups. I figure if I can get some dense moss going on the mounts and the back wall it might obscure the translations between the two. Just need to make sure the suctions are up to the task, else I’ll have to silicon.

Originally Posted by harpspiel

Keep in mind that evaporative cooling only works in low humidity environments, so it will work best if you’re pulling low humidity air from outside the enclosure through a wet pad into the tank. Assuming the air outside the enclosure is dry enough.

Also, I’ve had some success growing intermediate plants in warmish conditions, I think due to a good night temperature drop. My cuthbertsonii seems ok with days that can hit 90 if it drops to mid-70s every night. This is easy for me at a mile high, but you might also be able to get there with a combination of lights off, evaporative cooling and an open window...

The only thing I do not recommend is relying on sunlight, even a little direct sunlight can cook a tank really fast, and indirect light through glass would only work for pretty low light plants.

The warmest time of year here is also the driest so that will favor the evaporative cooling. Ideally The air will be pulled in through a cooled metal channel before the it is pulled through wet LECA dropping it further, and then into the tank. I’m working on design, but hopefully housed in a clay vessel.
I’ve heard that so long as I can get an adequate drop at nigh most the plants will be okay. Within the tank I’ll be circulating water in the bottom and maybe create a discreet spot for a couple ice packs if I run into issues. Also
I’m hoping through all of these elements and having it sealed well, insulated back exterior, I can manage 50 degrees at max efficiency. Internally I will have enough air to give the plants some sway.

I’ll keep this updated especially when I sort out this cooling unit.

Thanks 🙏 Excited to get everyone throughs, making sure I don’t overlook anything

[harpspiel]

Originally Posted by Jmbaum

I’m hoping through all of these elements and having it sealed well, insulated back exterior, I can manage 50 degrees at max efficiency. Internally I will have enough air to give the plants some sway.

Best case scenario, evaporative cooling drops the temperature about 20 degrees (I live in an area that primarily uses swamp coolers for cooling). That's with an ambient humidity of 20% and good insulation. I would recommend insulating 3 walls and the top of your tank, not just the back, since single pane glass has a terrible R-value. I still highly doubt you'll get down to 50, so you really should monitor your temps for a while before adding any cool-growing orchids.

[Jmbaum]

Originally Posted by harpspiel

you really should monitor your temps for a while before adding any cool-growing orchids.

Absolutely going to monitor as I get the moss and intermediate growers going.

I'll be up against the odds, but if my intake is metal (copper ideally) with lots of surface area, i'm hoping i can prechill the air before it goes through the evaporative process that will be housed in terracotta. I may end up running it through a physics simulator just to see theoretically how far off I am. Also will be able to calculate the heat sink of water at the bottom. So many variables depending how well I can seal the system. One draw back I'm seeing is that if my heat sinks have absorbed all day then It might be harder to drop it at night, should it be a warm night.

You are right, I really need to consider insulation on more than just the back expanse. I'll do the bottom and up 6 inches and the side the equip feeds in.

What species have you done well with? and what can you think of that, youd term risky?

[Jmbaum]

NOTE: Just called over to Andy's and looks like I'll need a temperature drop of 20 degrees at night... that's good to know as I'm planning.

[harpspiel]

Originally Posted by Jmbaum

What species have you done well with? and what can you think of that, youd term risky?

Andy's site has very detailed information on temperatures, even for lots of orchids that aren't currently available. That being said, the origin of the particular clone seems to play an important role - I have a perpetually unhappy Dendrobium 'Aussie's Hi Lo' (cuthbertsonii x laevifolium) and a Dendrobium limpidum that almost died and is very slowly making keikis, both from Ecuagenera. I have a suspicion that they are from one of the higher elevations within the species' range. On the other hand I have a Dendrobium cuthbertsonii, which is renowned for disliking heat, but I bought it from a seller who says his temps soar into the 90s in summer, and it's doing pretty well. So it's important to ask the specific seller about the specific temps for the plant you are buying.

According to Andy's, the variegated Mediocalcar decoratum doesn't like temps above 80, but mine (not from Andy) has been doing OK in my paludarium with temps into the upper 80s and a night temp drop into the lower 70s. It also has the most wonderful pink edges to the white stripes, which you sometimes get with variegated plants in high light, but in this case might be mostly on new foliage.

I have lots of Pleurothallids, mostly "warmth tolerant", that are growing very well for me. Masdevallias will helpfully let you know about excess heat with leaf spotting or other leaf issues. Pleurothallids that do well for me:
Barbosella gardneri
Lepanopsis 'Michele'
Lepanthes calodictyon
Lepanthopsis astrophora
Masdevallia erinacea
Masdevallia ignea x discoidea
Masdevallia wendlandiana
Pleurothallis dressleri
Pleurothallis grobyi
Pleurothallis ornata
Pleurothallis prolifera
Restrepia brachypus
Restrepia dodsonii
Trichosalpinx chamaelepanthes

I have a Begonia darthvaderiana (not doing well) and a Begonia tropaeolifolia in a special setup in my closet - neither tolerates temps above 80. Before settling on my closet I walked around my house with a thermometer and found the absolute coolest spot, so now I can grow a few low light, solidly intermediate plants, but I don't think the closet gets the nice temp drop that my paludarium does.

Plants that I don't dare try, but wish I could:
Epidendrum medusae
Masdevallia veitchiana (and lots of its hybrids)
Some Sophronitis species (I have a happy cernua)
A few cold growing Pleurothallids

However, if your temps end up actually going down to 50, then you won't want to grow most of the plants I'm currently growing. My temps are 60-75 winter and 72-90 summer.

[Jmbaum]

Thanks 🙏 that is plenty of great information, I have a few of those species in my 20 gallon. With no direct temperature modification.

… masdevallia veitchiana is a must on my list as well as a number of dracula. Looking at creating a strong gradient with the height of the tank. Also spoke at length to Clint from orchid dynasty so I feel a bit better that he’s growing them in firmly intermediate house but directly in front of swamp cooler. There’s hope 😅

[Jmbaum]

Possible grouping zones and shape, trying to not block too much light coming down, but still have natural flow

Here’s some species that caught my eye:

Trichoceros sp.
Stelis oscargrouchii
lepanthes rhodophylla
dresslerella caesariata
lepanthes gargoyla
masdevallia coccinea
masdevallia ignea
masdevallia veitchiana
Dracula andreettae
Dracula roezlii
Dracula vespertilio
Andinia dielsii
Platystele hirtzii