Purple leaves: Cold damage, Insect stress, too much light, magnesium or phosphorous

[K-Sci]

Originally Posted by Shadeflower

Last update.

Although I have a million things to report including getting rid of the reddening to some extent I can tell I haven't been able to convince anyone.

Shade, you did not state your thesis in this post, so I may not correctly/fully understand what you want to convince people of. This reply is based on my best understanding, which may not be completely right.

I think the source of the apprehension about purple indicating a nutrient imbalance is that purple stems and leaves are very well known to occur due to lower temperatures (as in the fall), high temperatures, or strong light. There is a genetic component too, as some orchids are more genetically predisposed to developing purple pigments in vegetative segments. I have a dark-flowered dendrobium that develops purple coloration every fall and a Neofinetia falcata 'Hokage' (火影) that is collected precisely because it develops purple on its leaves in the fall. In my view a small amount of purple or red in an orchid's leaves is an indicator that ideal lighting levels are being provided.

Okay, it is true that the papers you've cited in past threads show that red/purple leaves and stems can be caused by certain nutrient deficiencies. I didn't know this and you've definitely convinced me that this is a fact. But because the purple can also be due to norm al causes, the discoloration can't be used as a reliable diagnostic indicator for proper nutrients.

I was watching a youtube video with someone losing some leaves on their orchids and asking why. I know why but I also know said person from Orchidboard and know they would not listen. So why even ask..?

You've piqued my curiosity. What is the cause and how do you know it could not be a different cause.

An unforseen consequence of this experiement is that growth has dramatically increased. But pseudobulb size has increased too! Who knows what that will result in.

All my observations are wrong but a picture tells the story better than any opinion - in my opinion so here I will show an example of a pseudobulb that has practically doubled in size since changing what I was fertilzing.

What parameter did you change?

So ironically the bulb is still purple but I think in time that might get greener,

How do you know if the purple goes away due to your experiment, or normal seasonal variation in light and temperature?