Hi,
I recently got a Cattleya orchid and I was planning on transferring it to a freshly made concrete pot. Is concrete safe for orchids or should line the insides with plastic? I read freshly made ones have higher pH/alkaline. Not sure if that would cause any issues with the roots.
Thanks!

How big is your plant in comparison to the pot? I didn't think concrete pots came in small sizes. Is there a reason for using it rather than a plastic or terracotta pot?

I wouldn't line the insides with plastic, as this will probably trap too much moisture. I would expect the concrete to behave similarly to terracotta in that it will draw the water away from the plant and provide additional cooling for the root system.

You could also try soaking the pot for a few hours/days (not sure how long it would take to leach the majority of the free lime out) and then measuring the pH to see if it's too high.

Fresh concrete is harmful to plants. Wash your pot with vinegar to neutralize the lime more quickly. I'm not sure what a Cattleya would think of a concrete pot.

I would NOT use it directly to plant in. It will take some time to "season" concrete where it potentially will not effect the orchid.
Like Australis, I expect these pots to be too large leading to watering/moisture problems.
Why not use a clay or plastic pot to hold the orchid in and then slide it and the plant into the concrete container??? In this way you could easily see what happens with the roots as they grow out of the pot and make contact with the concrete. If the new green root tips turn brown fairly quickly, then you'll know that concrete is not useable as a pot. The damage to the orchid would be minimal as opposed to planting directly into it!

Could you post a photo of the pot? Is this something like a hypertufa container? I would always soak fresh hypertufa for a week in a strong vinegar solution - maybe 1 cup of white vinegar to a gallon of water to neutralize it.

There are several places offering Hypertufa pots for various types of plants. Manufacturers claim that the pots are great for cacti, succulents, tropicals and orchids! At least that is the claim.
However when I search for any comments or research on orchids in these pots, nothing comes up. Not a single word pro or con. They do say that they hold extra water so you have to water less often. Ah, that means a good pot for "lazy people", people who can't remember to water. I don't think that a pot holding water longer for a Cattleya is a good idea because they need to dry out between waterings! This type of container would be counter productive!
And since the number one ingredient is Portland cement, that throws up a HUGE caution flag for me.

I agree and would never use them for anything other than succulents but that is because they drain so quickly. I cannot see them holding moisture at all. However, different recipes can be used, perhaps someone could add something to make the mixture waterproof??? Too many variables/questions here.

Thank you for the responses. I have a mold for making small geometric pots and it's about the same size as a 4 inch terracotta pot. I went with concrete purely for cosmetic reasons. Right now it's growing on a bark substrate in a plastic pot with drainage holes. I wanted to switch to concrete because I thought it would soak up any excess water. (Though there's little chance of that as I've been watering it with a couple of ice cubes a week)
I like the idea of soaking the pot in vinegar solution. I'll do a bit more research on that and see if that's would be a good fit. Otherwise I might just put it in a terracotta pot. Thanks again for the help.

Ice Cubes?

NEVER water an orchid with ice cubes!
These are tropical plants, ice cold water is not good for them.
There may be impurities in the water/ice that accumulate.
The ice cube method only waters the top roots. Roots below that level never get water and die back.
If you fertilize the orchid, you are suppose to flush out salts from the fertilizer with plain water. There is no flushing with ice cubes!

If you have to water any plant, water it!!!

I've killed a couple of cactii in the past by over-watering so I'm scared to just pour water on any plant now. So I've been placing an icecube on top of the substrate. I've had this one for a couple of weeks now. I haven't fertilized the cattleya yet but I have those orchid plant food spikes (From Miracle-Gro). The plastic container it's in has good drainage so would it be safe for the plant if I run water through the substrate until it's soaked?

Also after reading the comments here and doing a bit of research on cement/concrete containers, I think I'll keep the cattleya in its current plastic container but I'll make a cement container to fit the plastic one inside it. That way I can simply take it out for watering and put it back in it after the excess water has drained off and not have to worry about lime affecting the plant.

Hmmm... skip the plant stakes too.

just my 2 cents worth ( as I grow a few Cattleya plants) .
Save your pots for another kind of plant. Plant your Cats in a clay pot or mount them or even use a plastic pot with lots of holes.

I agree!
Perhaps it might help you understanding how most tropical Orchids grow, here is a link regarding their epiphytic character.
http://www.orchidplantcare.inf...

sugarcane said:just my 2 cents worth ( as I grow a few Cattleya plants) .
Save your pots for another kind of plant. Plant your Cats in a clay pot or mount them or even use a plastic pot with lots of holes.

Thanks. I think I'll keep it in the plastic pot it came it. It has a lots of drainage holes.

DaisyI said:Hmmm... skip the plant stakes too.

What sort of fertilizer does is best? Or does it need it at all? The plant food sticks I have 10-10-10 macro nutrients. I found one online that was 13-3-15. Most of the articles I checked suggested something with high nitrogen for bark medium.

The type of fertilizer isn't that important but, the discussion we had just recently in:

The thread "Happy New Year 🎊🎉🍾 and our Orchid Blooms in January 2019" in Orchids forum

would suggest a lot of us like Dynamite slow release in the red can.

The problem with the fertilizer you chose is the form. The spikes fertilze the spot you stick them so you have one spot of over-fertilized medium and all the rest of the pot has no fertilizer at all.

As a newbie myself I would suggest that if (and when) you do fertilize cut the amount stated on the package by at least half if not a quarter of the amount. So if it says to use a teaspoon per gallon then use 1/4 teaspoon per gallon. Two reasons. Orchids, in general, are not heavy feeders and during the short daylight hour winter months plants are not as actively growing as the are during spring/summer. So the 'need' for fertilizer isn't as great.

I use the Dynamite once in the spring and, if my plants are lucky, again in the fall. They missed fall this year because I ran out of Dynamite and by the time I bought some, it was too cold. Better luck in the spring Little Orchids!

LOL, you have so little rain there the pellets probably last far longer than they do in the southeast where anything outdoors gets thoroughly drowned regularly. I was lucky to get 5 or 6 months tops out of them in SC.