Its temps and UV...
Hawaii is warm and humid but their UV index is stronger since they are closer to the equator. The other thing is if you notice that Plumies in Florida and Thailand get better color than Hawaii again because of HIGHER temps and strong UV.
Lopaka is the one I would ask regarding this. Robert get AMAXING color, textures and shapes on his flowers cause he is in the steamy hot temps of South Florida. I know during summer the temps average in the 90s and HUMID and WET.

I don't get as many blooms for comparison as those of you in warmer areas but I've noticed that the flowers that open in July and August are more intensly colored then the blooms I get in Sept and early Oct. Temps during July & Aug are often 90+ with 90%+ humidity. Once it cools down and the humidity drops the colors of my plumies (and some passifloras) are more muted. Blooms I get indoors under HID lights are really washed out looking and not very nice but if I have a well developed inflo when it's time to take them in I'll stick them under the grow lights.

Ok guys and gals- this is tormenting my brain. Some thoughts. Hawaii is closer to the equator by a few degrees latitude than Florida and Thailand is closer than Hawaii by several (Thai=7-20N; Haw=19-22N; Fla=24-30N; so Cal=32-34N). People on my same latitude but farther from the ocean have greater colors than I but I have larger blooms. Thailand and Florida are near coasts that have north flowing currents bringing humid, tropical air. Hawaii sits in a warm ocean but has trades bringing slightly drier air( when the konas blow from the south, Hawaii gets sticky humid.) So cal is on a cold, south flowing current which brings cooler, drier air. So all the factors contradict to some extent. If it was UV Hawaii would be greater than Florida. If it were humidity coastal So cal would be greater than inland. If it were temps, Texas and the southwest would have the best color. So it would appear that like James said it is some mix of all these factors with still humidity being a very important one combined with the temps and UV. There are so many scientific questions regarding plumerias and no university doing studies which would ease our brains. I wish I really knew this answer. Bill

I'd like to know what role night temps play into it, or temperature differentials between day and night. For example some deserts have hot days, cool nights -- South Florida would have warm humid days and very warm nights.

I think warm nights have a lot to do with color development (and overall plant vigor), but what do I know?

Dave- you know probably as much as the rest of us. Night temps make some sense but what about Texas. I do not know how it differs from Florida as far as day/night temps and humidity. It would be really nice if some university did some studies on this and soil composition and soil temps and fertilizers so we could really see what is going on. Jack Morgan is the only one I know doing limited scientific testing but you would think that more knowledge would greatly widen the market for these plants into more difficult zones. All of us doing trial and error experiments on very limited funds has minimal impact. Most of our help for nubies is based on significant loss from our own mistakes. Testing would greatly cut our losses too.

Here's something else to think about:

Is it an increased biochemical/ enzymatic efficiency that results in stronger pigment deposition...or...is it simply the environmental influence on the pigment molecules?

Bill - didn't you surmise on another thread that enclosing an inflorescence in a plastic bag to simulate a greenhouse effect might impact the color intensity? And didn't someone else try this with poor results? That would indicate that it is a physiologic process determining color intensity, not environmental.

What this could infer is that these unknown environmental factors (heat, humidity, UV, etc) are directly up-regulating some biologic process.

You then have to wonder if a supplemental hormone can up-regulate these pathways without needing the environment? Has anyone ever tried a jolt of B-1 or similar concoction at the time of inflo maturity?

In a controlled experiment each of these factors can easily be analyzed but who the heck has the resources for something rather unimportant in the scheme of things?

x

x- You are correct about the plastic bag but many other factors could have been involved. Too much moisture, change in the gases in the bag, etc. I can't say this was a controlled experiment and as we know one bad result is not always the case. However, I did not run any tests so it was just a thought. This is exactly why I would like to see university testing where enough experiments and controls can be monitored to get some true results. I can hardly remember when to feed my plants let alone run accurate tests. By the way, speaking of B-1, my home depot had a gallon for $5. Bill

Agreed. Enclosing an inflo in a baggie would create more potential hazzards to the inflo than not. No air circulation, greenhouse effect from sun, etc. And then you're ingnoring increasing humidity to the rest of the plant.

I think you'd need to distribute the same variety plant to multiple growers all around the world in pots with similar soil/fert. Have them keep records for several years, of temperature (highs and lows), angle of sun, latitude, humidity levels. Then keep photographic records of blooms, inflo size, flower diameters, etc.

BTW, Texas nights are hot in summer, believe me. I lived in Texas for a few years.

I would suspect that warm and humid 'summers' with small swings in day/night temp (90º/75º) and somewhat dryer winters (but still warm) would give the best results.

Hi, all, I'm the one that did the little experiment with the plastic bag on the inflo. It sure didn't work, at least here in Ohio. It had oodles of buds on it and each and every one died. I never got a bloom on it. I won't be doing that again! Crafty

Sorry Crafty- I didn't mean for you to experiment. So many factors involved. Did you seal the bag to the stem or was it open at the bottom? Just curious. Bill

Hi, Bill, I misted the inflo lightly then sealed the bag to the stem. The inflo didn't grow at all. I removed the bag after 2 weeks, but it didn't save the inflo. I just kept picking off the dead buds daily. Oh, well, now we know, at least here in Ohio. BTW, I wanted to let you know that Psycho White is doing just dandy. Thanks again for the cutting! ;o) Crafty