day Time & Night Time Temps for Phals

[OzPhal]

Do Phals require a different temperature during the day compared to at night? I've got mine in a climate controlled environment where i can program temperature, lighting, day/night cycles, humidity etc and i want to get it right

[ezil]

Yes they do. It all depends on which phals. you grow. Some species are really picky. If it is hybrids you grow, the rule of the thumb is about 5 - 6 degrees C cooler at night, especially in the fall.

[Zoi2]

As the days get shorter decrease the temperature.
In my experience it has taken closer to a 15 degree change for the phals to initiate spikes. I do not have species however.
Joann

[OzPhal]

Thanks everyone, i've modified the conditions in the growth chamber to be at 28oC during the day cycle and drop to 18oC during the night cycle - i'm currently running 70% RH - should i drop that during the night cycle?

[Blueszz]

I would reverse humidity. Higher day temps, lower humidity, lower night temps with higher humidity. This is what I think happens in nature too.
So, I prolly would aim for 70% during the night and lower during the day. With enough air circulation I don't think 70% is too high to give you problems with lower temperatures.

Nicole

[Ray]

Dr. Yin-Tung Wang did a study at Texas A&M in which they found that phals don't actually need diurnal temperature variation to initiate spiking, but instead, need a 10°-15°F reduction in the average temperature for a period of one-to two weeks to do so reliably (i.e., to have it happen in the majority of the plants so exposed).

Granted, a severe day/night variation can accomplish the same thing as lowering the constant temperature, but from a commercial perspective, in which you need the plants in flower to sell them, it's simply not a reliable enough driver.

[OzPhal]

Originally Posted by Ray

Dr. Yin-Tung Wang did a study at Texas A&M in which they found that phals don't actually need diurnal temperature variation to initiate spiking, but instead, need a 10°-15°F reduction in the average temperature for a period of one-to two weeks to do so reliably (i.e., to have it happen in the majority of the plants so exposed).

Granted, a severe day/night variation can accomplish the same thing as lowering the constant temperature, but from a commercial perspective, in which you need the plants in flower to sell them, it's simply not a reliable enough driver.

So if you had a fully controlable environment from lighting, temperature, rh % etc what would your ideal cycle be? at the moment i have 12hrs @ 28oC, 12hrs @ 18oC although this is a gradual ramp up between those temperatures over the cycle. So they don't have long at either 28oC or 18oC. I can modify the cycles to have longer periods at 28oC and conversely at 18oC - it would just mean there would be a more dramatic change between the two temperature extremes - i guess you would get a fair variation of temperature at sunrise/sunset in their natural environment - but i don't think it would be a rapid 10oC drop. Would it be worth maybe bringing my lower temperature up to say 21oC? Also, in regard lower RH during the day and higher RH at night - generally would you see a lower RH during the day? I would have thought that the sunlight in tropical environments would cause greater evaporation i.e. higher RH%