"Claude" wrote in message
.. .
Thanks Ray!

My Phals are in active growing and they have all new growth of roots,
leaves
or spikes.

So therefore you're doing well, and there is no pressing need to change
anything except the size of your collection, and the size of your growing
area if it is too cramped. :-)

I did add a console humidifier in my appartement to raise the relative
humidity at first for myself, then I was just wondering about my phals.

This morning, I just misted my phals with some water and the RH went up to
60 %.
I think I will add some trays under my pots, just to give them a boost!

I wouldn't bother with them, except to catch surplus water from watering
them. That is, unless you are going to enclose your growing area. As Ray
pointed out, the effect of humidity trays is rarely measurable. The fact is
that if YOU can't measure the effect of a tray on humidity, your plants
aren't likely to either, so unless you take extra steps to reduce the loss
of moisture from the air around your plants, they won't get an extra boost
from it.

The only way you will get a measurable effect is if you create growing area
that has a small volume (such as that inside a terrarium - just take a
decent size aquarium, put a few cm of gravel in the bottom and put in enough
water to come just below the surface of the gravel. And then, with a canopy
on the aquarium, perhaps modified to accomodate a small fan to keep air
flowing (whether you recycle the air or not), you will see RH inside the
terrarium much higher than it is in the rest of the house. (yes, if you
don't recycle the air in the terrarium, you will have to add water more
frequently, but the loss of water will be controlled by the fan size and
speed, and unless you go overboard with the size and speed of the fan, the
loss of moisture from the growing area will be much slower than if you just
use a tray.)

Now, I am not saying that humidity trays can't be made to work. Rather, the
way most people end up using them will likely have no more than a 2%
improvement, and this is far smaller than the acuracy with which most people
can measure RH. This is effectively the same result that Ray described in
his report of his experiment with humidity trays. To make them work, you
have to go the extra distance to make the volume of air that the tray must
affect as small as is practicable. There is a huge difference in trying to
humidify a third of a cubic metre (the volume of a modest aquarium) and
trying to humidify 50 cubic metres (the volume of air in a modest sized
room).

The other idea I see often floated for improving RH near the orchids is to
place plenty of other plants near them. This IS a sound idea, but again,
its effectiveness will depend on the details of what you do. You have to
use plants that transpire a lot, which usually means one native to a
rainforest area and which grows rapidly (growth rate and transpiration rate
tend to be rather strongly correlated - transpiration is the combined effect
of the transport of water up the plant, primarily for the purpose of
transporting essential nutrients but also for maintaining turgour pressure,
and respiration, which produces water and CO2 as by-products, and both tend
to be high in rapidly growing tissues). I doubt you'd see a measurable
effect if you used cactus. A modest, densely planted herb garden, OTOH,
probably would have a measurable effect (depending on the herbs used). But I
could be mistaken in this, as I haven't taken the time and other resources
to do my own experiments on this.

Cheers,

Ted