Evaporation or Plant Uptake??
 

Considering you got your culture totally on the mark... how much of the resrvoir loss is truly from plant uptake??

For example 40% Plant uptake 60% evap??

I know this also depends on relative climate in your area and greenhouse vs. outdoors vs. indoors..

But lets use the example of indoors on a west windowsill a paph..

That question still cannot be answered precisely, as there are too many variables, they all change on a daily basis, and some simply cannot be adequately quantified.

• What is the temperature profile?
• Relative humidity?
• Latitude (it affects the sun's angle, hence warming)?
• Season (ditto)?
• Air movement?
• Pot dimensions?
• Type of LECA?
• Size of plant?
• Specific species or hybrid?
• How well established is the plant (i.e., how well developed are its S/H roots and do the extend into the reservoir)?

Sorry for the question but I was just noticing how some of my s/h plants are uptaking more water than others..
I guess there are way too many variables to really know! :blushing:

I have 2 Phals, and 2 Oncs in S/H. Conditions are the same for all with the Phals receiving slightly less light than the Oncs. I have to water the Oncs twice a week as they will drain the reservoir in about 3-4 days. The Phals will still have fluid left in the reservoir after 7 days. HTH! ;)

Wouldn't it be fairly easy to find out by pouring the same amount of water in two hydro pots that were exactly the same and right next to each other... the only difference being that one had an orchid and the other didn't?

After a couple days you could pour out the water in both pots and measure the difference. The difference would be how much water the orchid had absorbed.

That scenario might give you just the opposite results! I'm not saying it would, but consider this scenario:

Let's say the plant is very well established, and the root system is really good. Then you get a period of gray, cool days, so the plant really slows its metabolic rate, so slows its water uptake accordingly.

Meanwhile evaporation is ongoing from its pot and the "control" pot with no plant. Oops...the root system of the plant is filling up some of the void space in the pot, so there will be less air flow and less evaporation.

At the end of your couple of days of testing, more water would have evaporated from the control, and it is conceivable that it would appear that the plant put water back into the pot!

...just too many possible variations.

My paph and masdie seems to need watering all the time from what I can tell... of course they are in a warmer room than other orchids of mine.. My phals and others seem to uptake rather slowly... but could be cause i just transferred them like 3 weeks ago..