This Could Be Why Your Healthy Phal Isn't Blooming
 

After browsing through RJ's thread and seeing that some otherwise healthy plants are refusing to bloom, I did some research and came across some interesting studies.

The results of these studies showed that, at least in the cloned hybrids used in the experiment, a day/night temperature fluctuation had no effect on spike formation.

Instead, a maximum daytime temperature of 26°C/78.8°F, regardless of nighttime temperature, caused plants to develop a spike after around 30-40 days.

Plants produced the most flowers at maximum daytime temperatures of 20°C/68°F, while daytime temps higher than 26°C/78.8°F actually inhibited the plants from flowering.

Bottom line: Keeping your Phalænopsis too warm during the day could be preventing it from blooming. This is a real break from what seems to be the common advice of day/night temperature differences. If you've had trouble so far, this could be the reason why!

Here are links to two studies:
http://www.ecaa.ntu.edu.tw/weifang/l...-flowering.pdf
http://www.hrt.msu.edu/faculty/Runkl...ering_2009.pdf

Hmm... interesting ...

So, if these studies are correct, I won't see spikes until spring. Interesting. I also noted that when I went to the OS meeting this week, there were no one had phals in bloom. Cattleyas, paphs, a couple of bulbos and a neofinetia falcata were in bloom. That was it.

You could turn the thermostat down to 72°F and see what happens!

Once the temps plummeted about a month ago, 5 of my 9 mature phals, all on windowsills, have put out spikes. Of the remaining 4, 3 are not currently healthy, and one - not sure what its problem is; it's growing leaves and roots quite happily, but no spike in sight. Maybe it's just slow.

The lower temps haven't slowed down my phal seedlings, either - I have 2 flasks' worth, still putting out roots and leaves. I'm beginning to think that extra heat is over-rated except maybe for vandas.

We keep our house temp at 20 deg. or less; the programmable thermostat goes down to 18 during the day and at night. But on a sunny day, the windowsill can get to 25-26 very easily, and the seedlings get the most benefit from that.

The overall low temp idea is deliberate, however - it's easiest for gh operators to ensure that the plants bloom by certain dates (Christmas, Valentine's, Easter, Mother's day) if they can control initiation of flowers through temperature and light levels. So if all they have to do is put some phals in a cold dark room for 2 weeks, 3 months prior to the scheduled shipment date, they have ensured themselves far more sales than if they had to take a chance. So a lot of plants are bred to initiate blooming through a change in conditions. Poinsettias, Easter lilies, epiphyllums...

We keep the house at 72 in the winter and have a programmable thermostat that shuts off the heat at night. I may have slow growers here. I also just cut the spikes on these in September. The ones that I didn't cut spikes on are still in bloom. So that may have something to do with it too. All the ones without spikes are still growing leaves and roots.

I agree with this cause my apartment is not heated very well so its in the 60's most of the time with little or no change of temperature at night at all and most of them spiked specially the ones by the windowsill where it's brighter.

Ah! Probably does! This would only work for a healthy phal that has been out of bloom for awhile, I think.

Plant metabolism and chemical processes can certainly be affected by temperature, but the maintenance of elevated temperature, by itself, as the reason for not blooming, might be misinterpretation of data. Consider that many phalaenopsis species are indigenous to equatorial forests, so experience elevated temperatures pretty much year round, and they bloom reliably. Let us also not forget that not all phals require temperature variation to bloom.

It turns out that the old "10-15 degree day/night temperature drop" adage is apparently also a misinterpretation: while at Texas A&M, Dr. Yin-Tung Wang showed that it was not the day-night temperature difference that was important in phalaenopsis blooming, but that they required ten day to two weeks of an AVERAGE temperature about 10-15 degrees cooler than that at which it had been growing.

Back in 2011, I tracked the daily highs and lows here in Bucks County, PA, and found that 222 out of 365 days of the year had a day/night temperature difference of fifteen degrees or more, occurring in every month, but I did not see a continuous stretch of the average being that much lower until early October, and sure enough, about six-to eight weeks later, spiking began. I for you want to see the data, it is here: http://www.firstrays.com/Phal_spiking.htm


Ray Barkalow
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Very interesting article and chart, Ray. I have experienced this with my own phals, most of which are the white/pink/purple variety, and are spiking within the last few weeks.