How cold does it need to be for spike

[camille1585]

Despite what is repeated over and over here, Phals do not need cold temps in order to spike. What they need is a general cooling down of both day and night temps and not an absolute minimum temperature. Commercial growers can control spiking by manipulating temperature, and they never get the greenhouses so cool (it's also too expensive to do it in thesummer months).

Most of my phals are spiking now, (some even started 6 weeks ago) and the temperature has never gone below 20C (68F) at night. The ones that spiked earlier never experienced below 23C (74F). My new apartment is very well insulated...

This article explains very well how temperature is manipulated to favor growth or spiking: http://www.hrt.msu.edu/faculty/Runkl...sis_Part_3.pdf

[Ray]

Thank you, Camille!

It is neither the minimum temperature, nor the more commonly misapplied "day/night temperature difference" that initiates spikes in phalaenopsis. The key is about two weeks of a 10°-15°F reduction in AVERAGE growing temperature.

If you've been 100° days and 80° nights (average = 90°), you'll need to expose the plants to an average of 75°.

If the average was 75°, the reduction will need to be 60°.

If your normal average is lower than that, you're growing the plants colder than they prefer.

When Dr. Yin-Tung Wang, then of Texas A&M published that, I tracked my own greenhouse conditions to test that. Read my results here.

[Vanda lover]

Phals don't need a lot of light, so an East window is ideal. I just put mine on the sills and they get chilled from the windows. Since all my sills are full, most of my phals are on North windowsills. They bloom fine but with perhaps a few less flowers than they would have if they were on an East sill.