Growing vanda roots upside down
 

While I am here I can as well annoy you a bit more with another question.

I have earlier complained that my vandas are not very eager on growing new roots.
I saw a couples of movies on YouTube where people were hanging their vandas upside down when they had almost no roots at all or just one little tiny root.
I do not remember the words they were using but the explanation was something like "the growing hormones (or energy ?) that the plant is producing is striving upwards so if you hang the orchids upside down it will help the roots start growing"... Or something similar.
Is that true ?
Does anyone here have any experience from doing this ?

I see where they are coming from with that, but that's not how it works... And a fine example why relying on youtube armchair experts for advice is rarely a good idea.

There is indeed a bottom up (and top down effect of certain hormones). The most important example of this are auxins and cytokinins which interact with each other. Auxins are produced in the tips of the shoots and are transported via the phloem to the roots, stimulating root growth. Cytokinins are produced in root tips, and while they tend to block root growth, they are transported upwards via the xylem (transport of water) and promote stem/leaf growth. The balance of auxins to cytokinins in the plant is what will determine what type of growth will 'dominate'.

Basically there are 2 main things that are wrong with the youtube theory: 1) root growth is mainly promoted by auxins, which travel downwards (not upwards). 2). Putting a plant upside down will not change the flow within the plant. The xylem will still continue to transport water from the roots to the rest of the plant, and the xylem will still continue to circulate assimilates throughout the plant. Aside from that, the plant is still subjected to the influence of light and is going to waste energy trying to grow upwards again. I even searched for scientific literature on the subject, and as far as I can tell there is no proof/mention anywhere that hanging a plant upside down is beneficial...

You normally should be able to promote new root growth by keeping the plant in high humidity, and application of some sort of kelp product could help as well.

I agree, I tried upside down with 2 vanda mokara for a month (whatever they are called now) as they have no roots what so ever. I think the seller just chop off the top of the plant and sell it without any air roots but the plant has a bunch of old flower stalks between leaves so I don't know if it can produce roots at all. I even tied coconut husks to the bottom stem while hanging it upside down to give more humidity but not a single green nub showing. Now I am back putting it in clay pot with one big lava rock and a little bit of moss to try for humidity. I had it in a jar with moss and had a plastic bag covering the leaves but the wind knock it off the table and broke the jar.

there is a simple reason for hanging vandas with little roots upside down when trying to make it produce roots but it has nothing to do with the plant actually producing roots better like this.

The reason growers originally did this which might have gotten lost in translation on youtube is because the plant needs the gets sprayed lots daily to prevent it drying out but it need to stay airy to dry out enough so hanging it upside down prevents water pooling in the leaf axils.
If the plant is upside down you can hose it down with a hose as much as you want, all the water will drip down, if the plant were the right way up you would have to dry the leaf axils every day to make sure no water has pooled there after watering as a rootless plant will be weak. So that is the reason..

Yes. I knew it was too good to be true.

The reason to hang them upside down that Orchidtinkerer presents seems logical. And then someone saw it and told others how to fast fix new roots and it ended up as an absolute truth.