Best temp for phal

[Sawdust]

I was wondering what is the best temp for phals. currently my temp is 70. I have just increased the light time as suggested in an earlier thread. thanks once again

[Roberta]

That's on the cool side for Phals. (At night that's fine) For daytime, they'd be happier somewhat warmer - a seedling heat mat might be your solution.

[Dimples]

Your average large flowered hybrids (think classic moth orchid) prefer a daytime high of at least 24C/75F and really enjoy 27-30C/80-86F, and warmer so long as there’s good airflow to prevent heat damage. Overnight lows down to 17C/62F are typically fine. They can tolerate a bit colder if they’re kept on the dry side but it’s not ideal.

The hot-growing types with the smaller star shaped flowers want to stay above 30C during the day. I don’t grow those but it seems they really sulk if they’re not kept hot.

[Roberta]

Of the star-shaped Phals, it depends... Phal violacea and Phal bellina and their hybrids love warmth. My GH isn't warm enough for them. (No longer have those, I tried...) But there are others with that form that are more forgiving. My GH goes down to 60 F/15 C on winter nights (fluctuates between that and 68 F/20 C, impossible to keep a small greenhouse more constant than that) , days usually around 75 F/24 C or thereabouts (a little more or a little less depending on what is happening outside) I do fine with Phal speciosa, tetraspis, corun-cervi, hieroglyphica, mannii, pulchra etc.

[Ray]

Some of the species - bellina, venosa, and tetrapsis, to name a few - prefer really hot conditions. Low triple digits and they are very happy, especially with super high humidity and deep shade.

[Mountaineer370]

Sawdust, I think a lot will depend on what type of Phals you are wanting to grow.

I grow hybrid winter-blooming Phals in my home at right around 70 degrees, no more than 72, day and night, all year round. I know this is not ideal, but I'm just posting to say that, for people who don't have the option of turning up the heat for them, it is still possible for them to do well. Even in these less-than-ideal temps, most of mine bloom every year. I'm sure, if I was able to provide higher temps, I would see more lush growth and more abundant flowering, but the plants and I have learned to live with what we have.

I did rehome my summer-blooming novelty type (star-shaped) Phals, bellina and violacia and their hybrids. They would bloom for me, but I just wasn't excited about getting one or two flowers once a year that lasted for just a few weeks.

I did keep my cornu-cervi that has been in almost constant bloom for a few years. I'm sure it would be happier and have a lot more flowers if it was warmer, but I can't bring myself to part with it because it's such an interesting Phal.

[Ray]

So relating back to the original question, there is a big difference between "ideal" and "what can they tolerate?", and every individual must decide where they want to be in that spectrum.

Based upon my observations of phals grown by folks on four continents, the absolute best was a grower with a greenhouse dedicated to them - 100°+ in the summer, saturated humidity, and algae so thick on the glazing it was downright dark. He let them get down into the 70's to set spikes, then boosted the temp over the winter.

Personally, I'm not willing to dedicate that much effort, so they'll have to be happy (or not) with what I give them.

[dbarron]

As a rule, they're (hybrids) pretty tough or there wouldn't be so darn many of them in cultivation everywhere. Ray hit the nail on the head of what they prefer over what they tolerate.
Some of the species or hybrids there of, are a lot more finicky and require higher temps to even live through the winter (let alone thrive).