Temperature and Spiking Experiment

[orchidsarefun]

thanks for all the input.
It's been about a month - and nothing as yet. I have seen leaves begin to change colour - going ( more ) purply. That could be do to with the light - they are further from the light than they were upstairs. Maybe they are going purple from the cold ? . Some roots did die back, but on the whole they are mostly green-tipped and healthy. My basement is fairly humid - 55% - so maybe that is keeping the roots ok. Leaves are growing fine.

[lotis146]

Really interesting leaves! What a strange development. Do you adjust the light duration for the season?

[Ray]

The experiment will confirm already well-established knowledge.

Quite a few years ago, Dr, Yin-Tung Wang, then at Texas A&M, proved that exposing phalaenopsis to a 2-week period of 10°-15°F reduction average growing temperature reliably caused the initiation of flower spikes some six- to eight weeks later. Returning them to the elevated temperatures after that treatment led to the best spike and flower development.

Out of curiosity, back in 2011, I plotted the average daily temperature, captured on a data logger:



The blue line represents the average temperature for each date. The red line is a 14 day running average temperature, which is the more important of the two curves. Note that we hit a peak in late-July/early-August of roughly 85°. You’ll also note that in early October, we finally got to an average temperature 15° lower. If Dr. Wang’s explanation of average temperatures was valid, we would expect that our phalaenopsis plants would start spiking approximately 6 to 8 weeks later, and in fact, that is exactly what happened, and then, as we approached a timeframe 6 to 8 weeks later than that, we saw the flower buds reach full development and begin to open.

[mtorchid]

Originally Posted by Ray

Note that we hit a peak in late-July/early-August of roughly 85°. You’ll also note that in early October, we finally got to an average temperature 15° lower.

Ray, How do you achieve this drop in temps in your greenhouse? I do believe that the main reason healthy orchids don't re-bloom for many folks is because the environment is too steady (comfy) without the stress on the plant to initiate bloom spikes. The dendrobium forum is full of examples where producing a winter rest period is a challenge for frustrated home growers. "A coddled orchid never blooms"- perhaps ?

[orchidsarefun]

So - after about 6 weeks in the coolhouse, I've swapped them with others from 'normal' growing conditions.
Normal is more light ( closer to bulbs ) and regular watering. The new batch will be kept in the coolhouse for 2 weeks....
It appears that there may be a spike developing on one, and a restart of a stalled spike on the same one ( so 2 on this plant ). Hopefully I get more.......and research quoted indicates I should, though windowsill/under lights growing conditions are a lot more variable than greenhouse conditions.


---------- Post added at 01:09 PM ---------- Previous post was at 12:57 PM ----------

Originally Posted by lotis146

Really interesting leaves! What a strange development. Do you adjust the light duration for the season?

I do for those under lights - roughly going from about 10hrs to 12hrs - Jan 10, Feb 11, March 12 and then Sept 12, Oct 11, Nov 10.
The leaves on this hybrid vary from green to purple anyway. Will see if the return to normal conditions has any impact on leaf colour.

[Ray]

Originally Posted by mtorchid

Ray, How do you achieve this drop in temps in your greenhouse?

By letting nature do its thing. I only control minimums via a thermostatically controlled heater.

[lotis146]

Intriguing Ray, thanks for sharing the research.

Orchidsarefun, that's great you've got some progress, hopefully you'll see even more sooner than later. And thanks for sharing you light schedule.

[orchidsarefun]

Another spike ? hopefully, as this would be a first bloom on my own cross. The pod parent spikes just above the leaf axis, not from the axis itself.

[lotis146]

Thrilling!!!

[orchidsarefun]

still only 3 with spikes. ( roughly 50% success rate so far, in about 2 weeks of normalised temps )
I am going to exchange the ones in the basement with others to continue the experiment. Its been about 2 weeks.
However I have got one on the plant stand that is spiking now without any temperature interference. ('freckles')