Question about temp & spikes

[butterfly_muse]

Good morning, everyone!

I have a question regarding spiking in orchids. I have read that orchids need a 20 or so degree temperature drop, but was wondering if it has to reach a specific temperature? Or if just the drop is enough?

Luckily, the Powers That Be have decided to finally let up with this relentless heat wave, and the past couple days have actually been...nice! It even got down to ~60 degrees overnight (in fact, it's 62 right now!!).

Looking at the forecast, it is supposed to be in the mid 80s during the day and in the mid-high 60s at night for the next week. I am wondering if I were to open my windows overnight, if that would be enough to make the plants go "WOOHOO PARTY" or if it would have to be for a more reliable, extended period of time?

I have also read that it takes a couple weeks, so I am wondering what exactly happens if there is, say, 8 or 9 days of temp drops but then the temp rises again...has anything at all happened to the plant? Will it help it? Hurt it?

Or does the temperature have to reach, say, the 50s? Or what if it were 90 during the day but 70 at night? Is that enough?

I'm confused. Help!!

[Bill U.]

Good morning!

This is and I think will continue to be a big gray area for phal culture. There are some sources that say they need the 20 degree drop for at least 2 weeks to up to a month and then, once spiking, return to normal temperatures. But then other sources say that many times phals don't need the temperature drop, but it can't hurt. I have read through several studies where there was the variance of light and also the "chilling effects" and there were percentages that responded to both. In another one of those studies, it showed that temperatures above the 85ºF mark caused a reduction in total vegetative growth and no spikes were produced- the theory was that the plant was conserving energy during the stressful time.(Exactly what studies they were, I don't recall- that was a long time ago. But if you are interested in reading them, I would try just doing an internet search and I'm sure you will come up with something.) So I wouldn't try to get things cranked up to 90ºF and then try and do a drop to 70ºF- that may end up shocking into not blooming.

Now for my experience- I have gotten several of my phals to spike without a significant drop in temperature. My grow area is normally around 75ºF during the day and will drop down to 68-70ºF at night, year round. I don't really do much to "force" them to bloom. I just kind of let them "do their thing" at their own pace and they normally will reward me with a lovely spike. In fact, I had a phal spike in the beginning of June (when it was hot, hot, and more hot), which completely flouted the temp drop- if anything it was a total temp increase!

There's my , hopefully you get more!

[Discus]

I guess it's plausible that what induces various phals might depend on their ancestry; I do recall reading that it was an overall reduction in temperature (rather than just at night) that seemed to initiate flower shoot development. I recall 12ºC/55ºF (presumably with fairly bright light) being the critical temperature to induce it, whilst temperatures above 27ºC and dim light prevented it.