Cattleyas - How Dry is Dry?
 

I've been growing and blooming orchids of all types for a while, but my weakest point is growing / blooming cattleyas. I'm not saying I'm bad at it, per say, but I am always trying to do better. I have grown and bloomed plenty of cattleya hybrids and some of the less fussier species, but they never quite look as robust as I see from some other growers.

I grow intermediate / warm cattleyas (Aclandiae, Nobilior, Amethystoglossa, Rex) under lights, in a large terrarium setup where I can control for temps and humidity. I keep the temp and humidity ranges where the plants should like them, summer 84F day / 68F night and winter 78F day / 62F night (humidity around 70-80% year round). As far as light goes, I give them the higher end of the range they should like (based on a par meter). So with all of that, I'd think they'd be set.

Going back to the question in the title, I'm beginning to question my watering regime, how dry is dry enough? The reason I ask, is that I've seen growers that have cattleyas sitting in what looks desert dry bark, and then I see cattleyas growing with moss completely covering the bark. I always try to get mine fairly dry, though not necessarily dry to the core if I were to unpot it, but... they definitely get dry enough that moss would never really take hold. Given my current humidity and temps, it might take 7-8 days for them to get bone dry, I probably water every 5-6 days when in active growth.

To complicate things, I have a couple of cattleyas in semi hydro which basically stay wet all the time, year round, and are doing great, including Dowiana and Perciviliana and I'm always curious why they need to dry out in bark, but can stay wet all the time in leca. I even bought a Warscewiczii from orchidweb that came in a plastic pot with pure sphagnum, which doesn't make sense to me at all - as soon as the new growth pushes roots, I intend on repotting that one.

Do you grow in plastic pots? For me, it has proven to be the most difficult option. I prefer them mounted over pots.

I get much better results in wooden baskets and I know that others do too. Clay pots also work quite well from what I understand.

So, yes, I do grow in plastic pots, but really that's only because that was the way I got them and I haven't repotted them yet. I just got a awesome lodigessii 'blue sky' in bloom and it came in a plastic pot, which I don't like, but it's not currently pushing roots, so repotting it now would end badly.

That said, I have repotted some of my plants into aircone plastic pots with bark - I've had good results with that setup and it also let's me see what's happening with the roots. A couple of smaller seedlings I've gotten from SVO, came in plastic and are doing well - and I'm ok with them in those pots because I know after their next growth, I'll soak the pots and be able to slip the root ball with the bark right out of the pot and into something larger (and likely clay at that point).

I would say clay is probably my preferred as it does dry them out sooner, but even with that, my question still stands - do you let them dry out to the core before watering again, clay or otherwise?

There is no need for the plants to be dry at all.

If you look at the habitat info, many catts are exposed to moderate to heavy rainfall all year.

What you're dealing with is plants that have gown root systems "attuned" to whatever they are in - and those are different. For the most part, I would think you could "pick one" medium/growing method and convert most of the plants to that for simplicity. Yeah, there might be an oddball here or there that will be better off treated differently, but that's part of the nature of orchid-growing.

It varies tremendously by plant. Species may be more demanding. No Cattleya wants to get dry for long while pushing new growth. Nobilior and aclandiae may be less tolerant of growing in pots, preferring roots to be more exposed.

Your conditions seem too cold to me but perhaps that because my Temps are 90-105 most summer days...

Beyond that, they are all in SH, so they never really get dry. I think its more about airflow than a need to dry.

1. The saying that Cattleyas need to dry out must have been coined at a time, when novice growers were killing the plants by drowning the roots. If the plants are potted correctly, they do not need to dry out at all.
2. There is significant difference between how small seedlings should be potted, versus mature miniatures, and versus mature standard Cattleyas.

For mature standard Cattleyas, it is important that they have good air flow through the pot. I use clay pots with a granular mix of bark & charcoal (1/2" to 3/4" size nuggets) plus a little coarse perlite. With this mix, I have to water heavily 3 times a week during the height of summer, and only once a week during the depth of winter - scaling up and down during spring & fall.

I am thinking it is a mix of your media and pots. It sounds like you may not be getting enough airflow around your roots. The roots can stay wet, as long as there is good airflow.

My Catts don't ever fully dry during the growing season, with the media "approaching dryness" between watering. I know that's a squishy definition, but it's as accurate as I can get it!

---------- Post added at 11:58 AM ---------- Previous post was at 11:57 AM ----------

I grow my nobilior exclusively in pots! They do very well with large media in clay pots under my conditions (i.e. hot).

Thanks for all of the replies. I've taken much of this into account and in retrospect it makes a lot of sense. In looking at some of my conditions a little more closely, I turned up the fans a bit more in my growing setup and dropped the humidity (my estimate was off, it was closer to high 80s on RH). I also increased the temps a bit to closer to 86 during the day, same temp at night.

I think for me, I was more wondering what I could do better, and it seems like based on what was said here, is maybe a bit warmer on temps and more air circulation since it's really not a matter of "it needs to be dry" as much as it "needs lots of air movement"... I think what's confusing is how there's so many places pushing that the media needs to dry out completely between watering. I'm assuming that they give that advice because people tend to overwater, plus, they may be growing on a windowsill with just about no air movement?