Adjusting watering schedule in greenhouse

[Rebecca817]

I keep the humidity in my outdoor greenhouse around 65-100%. I installed a patio misting system and run it for about 10-30 mins when the humility drops below 65%. Because of the high humidity, should I reduce my watering schedule (the typical 7 days)?

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[Ray]

I think not.

Water is the driving force for plant growth; the more frequently you soak the roots, the faster and better the growth will be.

Over the decades I grew in a greenhouse (oh, how I miss that....), I gradually adjusted my potting/mounting for each plant individually, so that I could water everything at the same time, as often as daily, if the weather warranted it, and my goal was to water frequently - easy, since I automated it.

My plants never grew better.

[riverrat]

I am dealing with the same issue. I have chosen to change the way my orchids are "potted" so that I can deal with the higher humidity. Air flow and media seem to be very important for me. Baskets work well...moss not so much. Orchids love the water but don't want to rot in it. I am a serial over waterer because I always want to do "something". In a high humidity greenhouse you do not want to retain too much water in the media. Also the air needs to move around really well. Mold loves still wet air.

[Ray]

Water is not the issue. Water held by surface tensionin the open spaces in the medium is the issue, as that suffocates the roots and kills them. Having a more open medium with larger voids so the interstitial water is minimized is the key.

Many growers in Florida use LECA precisely for those reasons, plus it absorbs water really well, keeping the root system moist even when the pellets appear dry.

[SouthPark]

Originally Posted by Ray

Water is not the issue. Water held by surface tension in the open spaces in the medium is the issue, as that suffocates the roots and kills them. Having a more open medium with larger voids so the interstitial water is minimized is the key.

Very nice discussion going on here.

I have read and heard people mentioning that the velamen portion of the root system staying wet for relatively long periods of time can drown the root. I haven't done any experiments before to see if this is true or not.

I'm just guessing that this might not be true, because velamen stays pretty much wet all the time in 'semi-hydro', right?

[Ray]

Correct - in semi-hydroponic culture and in nature!

[SouthPark]

Originally Posted by Ray

Correct - in semi-hydroponic culture and in nature!

Thanks Ray. Definitely happy that I got this sorted, as I had been thinking about this for ages, but never got around to asking.

[SouthPark]

Hi again Ray! From an AOS site, there's information that says "When this spongy material remains wet too long, the central core suffocates and begins to rot."

That is contradictory to the semi-hydroponic condition, right?

Also, there's a difference between stagnating trapped water (eg. waterlogged condition in some kinds of potting media) versus a semi-hydro condition, right? Such as oxygen level in the water? Semi-hydro is sort of dynamic - and water is able to keep moving --- perhaps slowly, but still moving all the time?

[estación seca]

In rainy humid seasons epiphytic orchid roots might be wet for months on end. Access to light, air and air circulation prevent rotting.

[SouthPark]

Thanks estacion ----- does this mean that these details : "When this spongy material remains wet too long, the central core suffocates and begins to rot" requires additional notes/considerations?

Sure - it could be considered as a general rule-of-thumb thing. But going down the various avenues should make for some really nice discussion.

Eg. in semi-hydro --- roots are indeed wet -- perhaps no light, but always wet, with usually adequate air and air circulation.

And - for an entirely different case - take some kind of potting mix having possibilities of water-logging and water saturation --- maybe no light and little air (or no air circulation).

Ignoring considerations of lighting for the moment. Then - is the difference between the air case and the no-air case going to boil down to one case has adequate oxygen in the water, while the other case does not?

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

This is just a friendly and really interesting discussion only.