How long cooling period for spikes?

[utah]

I was reading in the October issue of "Orchids". It mentioned cooling the phals at night to trigger flowering (into the mid 50s). Okay, I moved them all but am wondering how long I have to leave them in the unheated laundry room under lights?

I'd really like to enjoy my babies other than just when I'm folding socks.

How long do I need to cool them in the evenings before they set buds (they haven't even spiked yet)? Will they build life-long attachments with the laundry soap and mope around when I bring them back into my bedroom?

What signs should I look for when they are ready to immerge again from "time out"?

[BikerDoc5968]

I don't have an answer for the length of time to cool them. I have heard from someone who I believe is a reliable source that phals set their biological clock for flower growth sometime in late August/early September. Then they have to get up to speed and will grow a spike. Here in SE Michighan our nights have been in the low 60's to mid 50's for the past month and only in the last couple of days have we had frost, so I finally put the heater in the GH and maintain about 60 at night with daytime about 75+. I also think it isn't so much the low temp but the temp difference day/night....but there may be some other opinions....

[utah]

Makes sense, thanks. I don't want to move them to the greenhouse because of condensation, misting, and watering and the chance that they could keep moisture in their crowns despite my best efforts.

Hence the laundry room (poor babies) where I can hand water them, give them 12 hours of lights, and it cools down into the 50s at night but never colder than that.

Come on little ones - throw some spikes!!!

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[utah]

[mehitabel]

I don't think they need temps down into the 50's to spike. *Some* phals can *tolerate* tems in the 50's, but that doesn't mean it's good for them. In fact, temps that low can be damaging to phals.

A low of 60-65 at night should be enough for spiking a phal that is mature enough to bloom.

Most houses have at least one window that reaches that temperature in an unheated house (assuming you haven't turned the heat on yet. Even with the heat on, some windows are cooler than others.

Leave a mini max thermometer around different windows for a night or two til you find a good spot.

But I would keep them above 60 myself.

[terryros]

In a March 2004 AOS Orchids article by Lopez and Runkle "The Flowering of Orchids" a summary of the published literature on Phalaenopsis flower induction noted that photoperiod has little effect on flowering but that "most Phalaenopsis species and hybrids require a period of exposure to relatively cool temperatures ...".

In 2006, Runkle and Blanchard experimented in detail with what cooling means in Phalaenopsis flower induction with day lengths of 12 hours. The abstract of the article in the Journal of Experimental Botany can be seen at this link:

Temperature during the day, but not during the night, controls flowering of Phalaenopsis orchids -- Blanchard and Runkle 57 (15): 4043 -- Journal of Experimental Botany

A quick summary of this work would say that day time temperature reduction is more important than night time reduction. With clones of Phalaenopsis, they got at least 80% spike initiation with either 20C(68F) days/14C (57F) nights or with 23C(73F) days/17C(63F) nights. They could also induce the same spiking with constant 24 hour temperatures ranging from 14C(57F) to 23C(73). This obviously means that day/night temperature variation was not important!

Since most of us grow in conditions in which there is some diurnal variation in temperature, this work suggests that we need to focus on keeping the daytime temperature ≤ 23C(73F) and accept whatever night time temperature comes with that. Night time temperatures as low as 14C(57F) cannot be seen to harm spike initiation.

In my basement plant room in Minnesota this means having a window open in the Fall to be sure the room stays under 75F during the day. If we get a hot stretch, I shut the window and open the plant room door to let the basement air conditioning of the house help to cool the room. At night the open window means that I get temperatures between 57-63F.

I am helped by our cooler September and October temperatures in Minnesota so that I have been already vernalizing for over a month and most of my Phalaenopsis that are large enough to flower are already in spike.

[utah]

That helps a lot. Thanks!

[silberhaarig]

I'll just add my 2 cents worth. I set the thermostat in my house at 70 degrees F. daytime and 60 degrees F. for the night. Some of my Phals are in a bay window where the temperature is lower than the thermostat setting both day and night. Some of those Phals are now in bloom and some have new spikes.

In a back room I have a set of 2 fluorescent light tubes over a table full of orchids, It is undoubtedly warmer there than by the window,but the temperature certainly goes down at night. Several Phals there also have spikes. So I don't think an exact temperature makes the difference. It is just that there is a difference between day and night. I have found that my Phals are not as fussy as some articles would have you believe.

Nancy

[utah]

thank you!

[Ross]

My house thermostat is set to 67 during day and 62 at night. It switches at 9 PM and 8 AM. I do nothing special to induce blooming. I have one NOID hybrid with 2 spikes and a Phal Mini Mark Holmes with two emerging spikes. I think cooling is required but not a drastic or unreasonable cooling. The natural night time cool down for most homes should do it. Just my 2 cents.