Adjusting watering schedule in greenhouse

[Ray]

Originally Posted by SouthPark

So basically - roots drowning is due to not enough oxygen in the water? So dead drowned roots then brings rotting activity?

Almost.

It really isn't lack of oxygen in the water, it's general suffocation.

Unlike terrestrial plants that do almost all of their respiratory gas exchange through their leaves, orchids do much of it through their roots. Having the roots be wet all of the time is no issue IF there is plenty of airflow around them.

The trouble is that most potting media hold too much water in the spaces between particles, cutting off that air flow. (Hence the myth that "orchids have to dry out between waterings - if the lousy medium dries, those spaces open up again. Use a decent medium to start, and the gaps are large enough to never close when watered.)

And yes, it is dying tissue that rots, not healthy tissue.

[SouthPark]

Thanks very much Ray for teaching me and us orchidboard members these golden pieces of information. I'm definitely going to remember this....and will pass it on to others when appropriate. Thanks again Ray.