# Afternoon watering... a disconnect



## ChrisFL (Jul 22, 2012)

So, for many orchids like bulbos, they come from areas that get predominantly rained on during the mid afternoon. 

This is considered a universal no no in growing orchids. Everyone seems to be of the consensus that you water in the morning and let dry out during the day. 

Why the disconnect? I've been in rain forests at a variety of altitudes and things are still SOAKED at night, despite a temperature drop. 

What is it about being in "captivity" that makes this bad for plants?


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## newbud (Jul 22, 2012)

I water when ever. All different times of the day because I'm not very disciplined at all. When ever I feel the orchids calling me, I water. Sometimes that's 11pm, sometimes 6am. Phals; everything. I do try to blot out the phals if water gets in the crowns because of all the fear people have invoked in us. I've yet to see any damage or problem with this style of watering. My 2 cents.


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## Rick (Jul 22, 2012)

Chris

This was one of the "myths" that got me going on the low K stuff.

In my GH plants raised on low K high Ca/Mg don't die from rots when watered (or fogged on) during the afternoon or night.

The old reasoning was that some kind of magic airflow condition occurred in real rainforests at night to prevent "stagnation" of the water on the plants, or real rainforest rainfall is so strong that it flushed out pathogenic bacteria away from the plants.

My premise (that was supported in agricultural literature) was that high K leaf tissue concentrations (subsequently causing Ca and Mg deficiencies) reduces plant immunity to disease. 

The novel part of the low K study was that uptake of K in epiphytic plants is active and not passive. And given the access of unlimited amounts of K in the environment, most plants will grab as much as they can until toxicity occurs.


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## Candace (Jul 22, 2012)

Watering at night is not a 'no no' during the warmer months. At least I've never heard that. Typically, I don't water at night because of my schedule, but it has nothing to do with the plants. They must conform to my life and routine or get out:>


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## Rick (Jul 22, 2012)

One exciting piece of documentation was given to us by Stone (in Australia) which was a study of leaf tissue nutrient concentrations in in situ Panamanian epiphytes.

Maybe not so surprising, but exciting, was that the minority epiphytic species that had high K leaf content were ant associates (i.e. cultivated like humans cultivating corn). 

Potassium is primarily for sugar production in plants. We give corn high K to give is big sugar/starch filled ears of edible seeds. But corn is also a short lived annual that gets replanted every year.

The plants that ants cultivate have all kinds of little nectaries all over the plants to feed the ants (sugar). And maybe in a similar way, a lot of these "ant plants" tend to be semi deciduous, with explosive seasonal growth followed by a major seasonal leaf drop.


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## ChrisFL (Jul 22, 2012)

Very interesting Rick. 

Most people will pull their hair out reading this, but I don't fertilize at all. Ever. I have an intake fan that pumps fresh air through my system every 45 minutes for a 15 minute duration. 

And boy let me tell you, there ain't no magic airflow in tropical west Pacific rain forests. I honestly think the all out airflow needs of a lot of species have been greatly exaggerated. I think exchange with fresh air (personally) is MUCH more important that just air blowing around.


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## ChrisFL (Jul 22, 2012)

In fact, a lot of more delicate Bulbo spikes will blast in any air movement.


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## Rick (Jul 22, 2012)

ChrisFL said:


> Very interesting Rick.
> 
> Most people will pull their hair out reading this, but I don't fertilize at all.



Yes I also potted up a handful of plants in a shredded leaf litter mix from leaves in my front yard, that get NO supplemental feeding.

At the most we are looking at less than a year to six months, but so far they are growing just as good if not better than fed plants sitting next to them.

There is also a little old German lady in our orchid society that has been growing since the 1950's. Ran a corsage/cut flower business back when big Catt flowers were popular. She never has and never will give supplemental feeding. I've seen her greenhouses, and its full of huge specimen plants that have grown into the benches!


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## Lanmark (Jul 22, 2012)

There could be many reasons why indoor orchids often suffer from late-in-the-day waterings:


Atmospheric movement and air exchange is generally much better outdoors in the wild than it is indoors.


Hard-grown "wild" plants are often much tougher than pampered indoor plants, having been exposed to all sorts of adversity right from the very start.


"Wild" plants result as a product of natural selection or "survival of the fittest" instead of being offered the artificially-equal opportunity to start and thrive in a protected, sterile, agar environment before being manually selected for cultivation based on human esthetics.


The isolation of plants "in captivity" can exacerbate an infestation or infection by the very exclusion of otherwise naturally-occurring defenses and controls.


What Rick said about potassium.


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## Hera (Jul 22, 2012)

Another thought, plants in the wild certainly don't look as picture ready as our home grown ones. Most pictures of wild grown at least have mechanical damage and I would make the assumption that the ones affected by disease quickly succumb and rot away. We tend to expect that every leaf on a plant should be shiny and healthy. While it is a good indicator of good culture, wild plants never show absolutely no damage. A season of poor growing conditions in the wild would have a definite effect. That being said, even with good air movement in a greenhouse we are moving around the same volume. Spores of mold, fungus etc, and critters and their eggs are concentrated in a small space. I agree that wild plants are hardier as well.


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## Rick (Jul 22, 2012)

I think there's a big difference between a bit of mechanical damage hear and there in wild plants, and complete dead rotted plants in the GH.

We get to see more and more in situ pics of wild plants on this site, and lots of them are superior to greenhouse plants even with a few leaves out of place.

I spend plenty of time at shows and judging centers (where we should be seeing the cream of the crop), and high quality unblemished specimen plants are just as rare as perfect plants in the jungle.


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## Stone (Jul 22, 2012)

Having grown orchids both outside and in a glass house, I can say that there is a WORLD of difference in air movement. Even on an apparently still day, there is still more air moving than inside the g/house with 5 fans going flat-out! Let alone a sight breeze or wind. It would cost me a fortune to move that much air 24/7, so I water between morning to miday unless its a warm and windy night outside and I can leave all the windows open.


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## Paul Mc (Jul 22, 2012)

I have to say though, Ive read the same about watering your outdoor plants. Only do so in the morning to early evening. For the same reasons people have said Bout why to water orchids at that time. Does that have truth then?


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## gonewild (Jul 22, 2012)

One reason not mentioned is that orchids in the rainforest are not growing in pots or mounted on "unnatural media". Another is that it does not seem to benefit the plants to water them at night when growing under artificial conditions and it can contribute to serious problems.


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## gonewild (Jul 22, 2012)

Rick said:


> I think there's a big difference between a bit of mechanical damage hear and there in wild plants, and complete dead rotted plants in the GH.



We don't really see too many "rotting" orchids in the natural habitat. Probably because when a plant does get an infection it is decomposed within a short time.



> We get to see more and more in situ pics of wild plants on this site, and lots of them are superior to greenhouse plants even with a few leaves out of place.



That is because the photographer selects the beautiful plants to photograph and shuns the ragged ones.



> I spend plenty of time at shows and judging centers (where we should be seeing the cream of the crop), and high quality unblemished



All plants in the jungle are perfect! :drool:


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## Stone (Jul 22, 2012)

Paul Mc said:


> I have to say though, Ive read the same about watering your outdoor plants. Only do so in the morning to early evening. For the same reasons people have said Bout why to water orchids at that time. Does that have truth then?



In summer I water the shadehouse plants just before sunset every single day and they're are always dry (at the leaf) by morning. Mind you that our summers have less rain and lower humidity.


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## Rick (Jul 22, 2012)

gonewild said:


> it can contribute to serious problems.



Lance that was the point that started this thread.

How come only "serious problems" happen in GH when watering at night, but jungle plants survive (barring some "mechanical damage")?

Orchids have survived in jungles for millions of years getting rained on at all hours of the day, but the way individuals talk (such as "contributes to serious problems") suggest that you can loose a whole GH of orchids in a week by night watering.

I have a fogger set to a humidistat in my GH that generates considerable fog whenever the humidity drops below 70%. I know it comes on at night at times because I've been in the GH at all hours checking things out. But over the last 10+ years I've never had any all out epidemics. And since going K-lite I'm having very much fewer individual plant problems.


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## emydura (Jul 22, 2012)

Rick said:


> Lance that was the point that started this thread.
> 
> How come only "serious problems" happen in GH when watering at night, but jungle plants survive (barring some "mechanical damage")?
> 
> ...



I think what Lance was saying is that there are no actual benefits from watering the greenhouse at night but plenty of potential problems. I don't have anywhere near the rot problems I use to have but I wouldn't tempt fate by watering at night. I don't see why I would want to. CAM plants would be different but Paphs aren't one of those.


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## ChrisFL (Jul 22, 2012)

Let me also back up here. I see "at night" being tossed around. I'm talking about watering between 3-5 PM, when most rainstorms fire off in the Maritime Continent. 

If I water during the morning and have plenty of air exchange, the plants dry out. A lot of people consider that ideal, I don't based on what I've seen in the wild for species like bulbos. Leaves maybe, but not roots.


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## goods (Jul 23, 2012)

I grow in two different tanks, a regular terrarium and my modified fridge. I try to follow the old rule of watering only in the morning to let things dry out, but that wasn't possible for me last semester. My classes on Tuesdays and Thursdays started before the lights came on, and I wasn't home until 4ish. Since most of my plants are mounted, I watered everyday. Aside from my finicky B. nitidum, none of my plants showed any ill effects to the later watering. My terrarium has a ~1" opening in the top for air exchange and two computer fans, and the fridge has a small hole for minimal gas exchange but has heavy air movement inside.

I tend to not fertilize and use mostly rain or RO water when watering.


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## paphioboy (Jul 23, 2012)

It can rain continuously all night (after 5pm, through to morning) during the year-end monsoon period in Malaysia and some South-Eastern Asian countries. I think there is no reason for wild plants to NOT rot. I have bulbos in my collection who turn a black leaf or two after a really heavy downpour and some thinner-leaved species (Gongora) develop some black spotting, which I think is pretty normal for outdoor growing. You can NEVER have perfectly unblemished plants, wild or cultivated, if growing exposed to the elements. I suppose plants grown outdoors make up for the damage by extra vigour in the new season's growth. For example, bulbos grown outdoors in the tropics can complete 3-4 growth cycles in a year, but if grown in greenhouses, I think the growth cycle will be slower..


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## gonewild (Jul 23, 2012)

> Rick said:
> 
> 
> > Lance that was the point that started this thread.
> ...


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## gonewild (Jul 23, 2012)

emydura said:


> I think what Lance was saying is that there are no actual benefits from watering the greenhouse at night but plenty of potential problems.



That is exactly what I was saying.


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## gonewild (Jul 23, 2012)

ChrisFL said:


> Let me also back up here. I see "at night" being tossed around. I'm talking about watering between 3-5 PM, when most rainstorms fire off in the Maritime Continent.
> 
> If I water during the morning and have plenty of air exchange, the plants dry out. A lot of people consider that ideal, I don't based on what I've seen in the wild for species like bulbos. Leaves maybe, but not roots.



When I refer to "night watering" I'm refering to having the foliage wet with potential water collected in the crowns when the environment has switched to nighttime conditions.

I like to keep the foliage wet all day but try to have it just getting dry by nightfall.

Watering at night is probably less of a problem than having the crowns full of water that has been sitting stagnant for hours from earlier waterings.


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## Rick (Jul 23, 2012)

Would you agree that "contributes to serious problems" is quite a bit different in magnitude to "can potentially cause problems"?

I agree that most of us would find it cumbersome to water at night to make a practice out of it. And I also wouldn't it make it a practice myself. But I don't think it makes a difference if you water early AM or late afternoon either if you have healthy plants to start with.


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## Rick (Jul 23, 2012)

gonewild said:


> > It is not high humidity or the water that causes the "rot",
> 
> 
> 
> I agree with this too, but Helger Perner, is his newest AOS article blames high night humidity as a cause of rot in paph seedlings.


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## Lanmark (Jul 23, 2012)

gonewild said:


> One reason not mentioned is that orchids in the rainforest are not growing in pots or mounted on "unnatural media". Another is that it does not seem to benefit the plants to water them at night when growing under artificial conditions and it *can contribute to serious problems*.





Rick said:


> Would you agree that *"contributes to serious problems" *is quite a bit different in magnitude to *"can potentially cause problems"*?



I'd agree that "contributes to serious problems" is quite a bit different in magnitude to "can contribute to serious problems" which is not all that different from "can potentially cause problems"

:wink:


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## cnycharles (Jul 23, 2012)

one point about plants outside, getting hours and hours of rain and not rotting; usually the problem is having too much water that has no oxygen in it, and having standing water on leaf tissues that allows fungi to settle, and germinate. many or most fungi need high humidity or standing moisture to 'pop'; running water washes away most plant fungi spores. if the spore is not stable where there is not water, then it won't germinate (a relative description, there are likely some fungi that may need moving water to germinate.

water without air (the balance) can lead to lots of problems. plants in the greenhouse that have continually dripping water from a roof or hose leak often are larger than those around that are not getting the moving water that has oxygen in it, and the plant is constantly wet and the media saturated. often our books that have cultural info are written for northern, north american growers who have cool conditions and little air movement for a greater portion of the year, so generalizations get made as to what is the best 'culture' for home orchids. I think it was a few weeks ago someone was posting here that they watered all of their mounted orchids in the early evening, just like was happening in the wild in their neighborhood, and their plants were doing much better than when they were watering them early, or in the morning


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## Lanmark (Jul 23, 2012)

cnycharles said:


> often our books that have cultural info are written for northern, north american growers who have cool conditions and little air movement for a greater portion of the year, so generalizations get made as to what is the best 'culture' for home orchids. I think it was a few weeks ago someone was posting here that they watered all of their mounted orchids in the early evening, just like was happening in the wild in their neighborhood, and their plants were doing much better than when they were watering them early, or in the morning



Exactly!

There are many generalized guidelines to successful orchid culture including those which recommend only morningtime watering routines.These are not unbreakable commandments. They are suggestions based upon years of collective experience. It's always wonderful to hear from those who find success using alternate methods of cultivation, and these successes further broaden our collective base of knowledge.


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## gonewild (Jul 23, 2012)

Rick said:


> Would you agree that "contributes to serious problems" is quite a bit different in magnitude to "can potentially cause problems"?



Yes I would agree with that. But the meaning and magnitude changes with what words are used before each phrase. 
If you are referring to what I said, I think what I wrote was "_it can contribute to serious problems_" rather than _"contributes to serious problems"_. In that case the _"it can"_ lessens the magnitude. 



> I agree that most of us would find it cumbersome to water at night to make a practice out of it. And I also wouldn't it make it a practice myself. But I don't think it makes a difference if you water early AM or late afternoon either if you have healthy plants to start with.



You are correct it does not make a difference and in fact as I have said before I like to water all day long. The main point is to try to avoid wet foliage at night as a precaution to avoid problems. A few years back i had a lathe house in Peru with about 400 plants planted in baskets and I installed a mist system that came on every hour for one minute 24 hours per day every day. This was a mist and not fog, the foliage was wet all the time at night. Never a plant rotted in several years time. But I would not do that in a closed environment.


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## gonewild (Jul 23, 2012)

cnycharles said:


> one point about plants outside, getting hours and hours of rain and not rotting; usually the problem is having too much water that has no oxygen in it, and having standing water on leaf tissues that allows fungi to settle, and germinate.



Yes and when you do have wet foliage with standing water that is low in oxygen if you circulate air over the water the water will absorb oxygen. As you said the increase in oxygen content of the water inhibits pathogen growth. That is one reason to support the need for strong air movement in a greenhouse.


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## Lanmark (Jul 23, 2012)

gonewild said:


> Yes I would agree with that. But the meaning and magnitude changes with what words are used before each phrase.
> If you are referring to what I said, I think what I wrote was "_it can contribute to serious problems_" rather than _"contributes to serious problems"_. In that case the _"it can"_ lessens the magnitude.



:wink: ...as I pointed out earlier.


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## Ray (Jul 24, 2012)

An interesting thread, but we might also consider that "in the greenhouse" we have a fine little incubator for all sorts of pathogens, while limiting the natural enemies to them that occur abundantly in the wild.

Holger's comment that high humidity in the greenhouse increases the chance of rots might be more related that that than anything else, as by increasing the humidity, we may be improving the conditions for the pathogens.


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## Ray (Jul 24, 2012)

gonewild said:


> Yes and when you do have wet foliage with standing water that is low in oxygen if you circulate air over the water the water will absorb oxygen. As you said the increase in oxygen content of the water inhibits pathogen growth. That is one reason to support the need for strong air movement in a greenhouse.


Huh? (Sorry Lance, I have to disagree)

Gases have an equilibrium solubility in water that is determined by their concentration in the atmosphere surrounding the water, the temperature and pressure. That equilibrium concentration is reached pretty much instantly, even in water that has been intentionally "out-gassed" (and our irrigation water supplies are hardly that), especially with the surface-to-volume ratios involved.

Air movement does not change any part of the equilibrium conditions, so will not increase the oxygen content of the water.


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## gonewild (Jul 24, 2012)

Ray said:


> Huh? (Sorry Lance, I have to disagree)
> 
> Gases have an equilibrium solubility in water that is determined by their concentration in the atmosphere surrounding the water, the temperature and pressure. That equilibrium concentration is reached pretty much instantly, even in water that has been intentionally "out-gassed" (and our irrigation water supplies are hardly that), especially with the surface-to-volume ratios involved.
> 
> Air movement does not change any part of the equilibrium conditions, so will not increase the oxygen content of the water.



You could be right but I based the idea on what happens in a lake of pond when air moves across the surface. When air moves over water surface of a lake the oxygen level is greatly increased. The main reason is because the air currents makes ripples in the water and the surface increases to absorb more oxygen. Maybe the air movement does not effect small bodies (drops) of water of in the same way? But it probably does. As well when you refresh the air in contact with the wet leaf you are bringing in air that has a slightly higher oxygen content and as such the water would take a little more oxygen to try to stay in equilibrium. Anyway that is what I'm thinking at the moment.

When water evaporates what happens to the oxygen content of the remaining water?


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## ChrisFL (Jul 24, 2012)

gonewild said:


> You could be right but I based the idea on what happens in a lake of pond when air moves across the surface. When air moves over water surface of a lake the oxygen level is greatly increased.



The surface area to volume area of a lake is very different than water droplets: as Ray mentioned, they equilibrate with atmospheric gases almost instantly. 




> The main reason is because the air currents makes ripples in the water and the surface increases to absorb more oxygen. Maybe the air movement does not effect small bodies (drops) of water of in the same way? But it probably does.



It does not. Temperature, pressure, and pO2 determine how much O2 the water droplet can have dissolved in it. This equilibrium is reached almost instantly in tiny droplets. 



> As well when you refresh the air in contact with the wet leaf you are bringing in air that has a slightly higher oxygen content



This is pure speculation. We are talking about gases here. 



> When water evaporates what happens to the oxygen content of the remaining water?



It will remain the same, the water will off gas O2 to remain in thermodynamic equilibrium.


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## Ray (Jul 24, 2012)

I think the reason that a lake's overall oxygen content increases is because the turbulence brought about by the wind stirs the water, bringing the lower-content stuff up from below so it can become more oxygenated.

As Chris said, the low surface-to-volume ratio of a lake will slow the "re-equilibration" process, but if things stay calm, it will return to the overall average dictated by the conditions.


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## gonewild (Jul 24, 2012)

ChrisFL said:


> The surface area to volume area of a lake is very different than water droplets: as Ray mentioned, they equilibrate with atmospheric gases almost instantly.



I guess I would consider the water pooled in a Phal crown as a tiny "deep" lake.



> It does not. Temperature, pressure, and pO2 determine how much O2 the water droplet can have dissolved in it. This equilibrium is reached almost instantly in tiny droplets.



I'm not talking about tiny droplets of water but rather water pooled on leaf surfaces or in leaf axils.




> This is pure speculation. We are talking about gases here.
> 
> It will remain the same, the water will off gas O2 to remain in thermodynamic equilibrium.



When air currents replenish the air in contact with the water surface the air in direct contact with the water surface would have more oxygen to exchange. Just the reverse of when a rain drop falls through the atmosphere.


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## gonewild (Jul 24, 2012)

Ray said:


> I think the reason that a lake's overall oxygen content increases is because the turbulence brought about by the wind stirs the water, bringing the lower-content stuff up from below so it can become more oxygenated.
> 
> As Chris said, the low surface-to-volume ratio of a lake will slow the "re-equilibration" process, but if things stay calm, it will return to the overall average dictated by the conditions.



The water in the crown of an orchid plant is like a tiny deep lake is it not?
How much extra oxygen needs to be added to inhibit pathogen growth?

If you have no air movement in a greenhouse there is no surface disturbance but if you have a violent wind from a fan there is a lot of surface movement.


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## gonewild (Jul 24, 2012)

Along the line of air movement at night decreasing the chance of disease when foliage is wet....

As air moves across the wet leaf the water evaporates. As the water evaporates the remaining water is cooled. The cooled water will absorb more oxygen from the atmosphere. Water with more oxygen will have slower pathogen growth. Now add in the cooler water temperature and you have even less pathogen growth.


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## keithrs (Jul 24, 2012)

Ray said it..... Interesting thread!!!


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## keithrs (Jul 24, 2012)

gonewild said:


> Along the line of air movement at night decreasing the chance of disease when foliage is wet....
> 
> As air moves across the wet leaf the water evaporates. As the water evaporates the remaining water is cooled. The cooled water will absorb more oxygen from the atmosphere. Water with more oxygen will have slower pathogen growth. Now add in the cooler water temperature and you have even less pathogen growth.



I tend to agree with this...

Anaerobic bacteria thrive under moist stall air.... Hence anaerobic... Some growers tend to use too fine or allow there mix to break down too much, there for 'sealing' there roots off from air movement allowing 'bad' bactria too take over.

I like to believe that introducing aerobic bactria and to some degree fungi that 'eat' anaerobic into a greenhouse is beneficial along with very good air movement around the roots. 

Water holding to air capacity is super important for long term health of your roots.

EDITED FOR SPELLING****


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## Rick (Jul 24, 2012)

Ray said:


> I think the reason that a lake's overall oxygen content increases is because the turbulence brought about by the wind stirs the water, bringing the lower-content stuff up from below so it can become more oxygenated.
> 
> As Chris said, the low surface-to-volume ratio of a lake will slow the "re-equilibration" process, but if things stay calm, it will return to the overall average dictated by the conditions.



As noted above in a couple of posts lake/pond DO levels are all over the place, and a function of depth, temp, elevation, clarity (for light penetration to support photosynthesis), TDS. Typical surface DO's are full saturation or greater based on pelagic algae photosynthetic rates. Lower depths can be deoxygenated, and the demarkation can be abrupt. Otherwise known as the thermocline. Thermoclines are seasonal and can be disrupted or shifted by winds.

http://en.wikipedia.org/wiki/Hypolimnion

But breezes generating mild ripples have very little effect on overall DO content of lakes and ponds. But very little of the above has much to do with DO levels on damp leaves (or leaf axials).

Also as noted earlier DO saturation is mostly a function of volume/surface area/organic loading. Subsequently the DO levels in films on leaves is full saturation unless the leaf is already completed covered with a film of bacteria munching away on a film of organic (poop/sugar) media.


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## Rick (Jul 24, 2012)

keithrs said:


> I tend to agree with this...
> 
> Anti-aerorobic bactria thrive under moist stall air.... Hence anti-aerorobic.... Some growers tend to use too fine or allow there mix to break down too much, there for 'sealing' there roots off from air movement allowing 'bad' bactria too take over.
> 
> ...



Do you mean "anoxic bacteria"? Anoxic species don't kick in till less than 1 or 2 mg/L DO on thin film aqueous solutions, and you can't reach this level at normal atmospheric conditions without a tremendous organic load full of aerobes eating organic materials and using up the DO in the first place. I work in waste water systems using both activated sludge and fixed film systems, and the only way we can get the anoxic species to work under very heavy loaded systems (not the wimpy stuff on leaves in a GH) is to put the system in a full nitrogen environment to purge out the DO.

In general trying to blame the pathogen issues on oxygen content is not going to fly very easy since the conditions in our green house are still fully supporting normally oxygenated systems. (Nobody suffocates in their greenhouses at night).


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## Rick (Jul 24, 2012)

http://www.fluidfertilizer.com/pastart/pdf/36p16-19.pdf

Check out the above article on plant nutrition and disease. Looks at Erwinia and Botrytus infections in bean plants relative to tissue calcium concentrations.

If you compare tables 1 and 2 and put in light of the antagonistic effects of potassium on calcium uptake you can see how excess K promotes loss of resistance against two disease genera that are common problems in orchids.


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## keithrs (Jul 24, 2012)

I meant anaerobic bacteria.


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## Rick (Jul 24, 2012)

keithrs said:


> I meant anaerobic bacteria.



http://answers.yahoo.com/question/index?qid=20070622060405AAPb3YW

The above is good for the fast answer.


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## Rick (Jul 24, 2012)

keithrs said:


> I tend to agree with this...
> 
> Anaerobic bacteria thrive under moist stall air....
> 
> EDITED FOR SPELLING****



Afraid not. Moist stale air still has too much O2 to support obligate anaerobes.

Even the exhalation from human lungs still contains enough O2 to support aerobic bacteria. Minimal DO for supporting fish in EPA tox tests is only 4ppm. Aerobic activated sludge waste water plants typically run between 2-4 ppm of aqueous DO to minimize blower costs. From 1-2 ppm DO the falcultative anaerobes start to wake up. The obligates won't get happy until 0 mg/L. The crazy sulfur bacteria and methangenerators can't kick in until the sulfide concentrations build up to significant levels and drive ORP to crazy negative values. Sulfides can't exist in oxic environments without getting converted to sulfates.


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## Stone (Jul 24, 2012)

Rick said:


> http://www.fluidfertilizer.com/pastart/pdf/36p16-19.pdf
> 
> Check out the above article on plant nutrition and disease. Looks at Erwinia and Botrytus infections in bean plants relative to tissue calcium concentrations.
> 
> If you compare tables 1 and 2 and put in light of the antagonistic effects of potassium on calcium uptake you can see how excess K promotes loss of resistance against two disease genera that are common problems in orchids.



Thats ineresting. I always wondered why they recommended using Calcium hydroxide with urea sprays!!
The problem of getting Ca into plants is still there. Aparently it can only be taken up by (growing) root tips so that suggests spraying rootless plants with fert could be counterproductive?? ( loading up on N and K and Mg without Ca to balance them).
And feeding when the plant (roots) is inactive could throw leaf nutrient levels out of balance as well.
I think I read Ca. foliar apps. did enter the leaf somewhat but was totally imoblie so of little benefit. 
So maybe just as important as reducing K is to supply Ca when the plant is receptive OR not feeding N, K and Mg when its not?
Easier said than done!!!


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## Stone (Jul 25, 2012)

Rick said:


> Afraid not. Moist stale air still has too much O2 to support obligate anaerobes.
> 
> Even the exhalation from human lungs still contains enough O2 to support aerobic bacteria. Minimal DO for supporting fish in EPA tox tests is only 4ppm. Aerobic activated sludge waste water plants typically run between 2-4 ppm of aqueous DO to minimize blower costs. From 1-2 ppm DO the falcultative anaerobes start to wake up. The obligates won't get happy until 0 mg/L. The crazy sulfur bacteria and methangenerators can't kick in until the sulfide concentrations build up to significant levels and drive ORP to crazy negative values. Sulfides can't exist in oxic environments without getting converted to sulfates.



Or...put another way....Still too much air for the little suckers.
If you fill a can with wet soybean meal and put an air-tight lid on it, well...you'll have what you're looking for..:evil:


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## Rick (Jul 25, 2012)

Stone said:


> Or...put another way....Still too much air for the little suckers.
> If you fill a can with wet soybean meal and put an air-tight lid on it, well...you'll have what you're looking for..:evil:



yes:evil:


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## keithrs (Jul 25, 2012)

Rick said:


> Afraid not. Moist stale air still has too much O2 to support obligate anaerobes.



Anaerobes like Erwinia can live in o2 environments. Why can't others?


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## Rick (Jul 25, 2012)

Stone said:


> Thats ineresting. I always wondered why they recommended using Calcium hydroxide with urea sprays!!
> The problem of getting Ca into plants is still there. Aparently it can only be taken up by (growing) root tips so that suggests spraying rootless plants with fert could be counterproductive?? ( loading up on N and K and Mg without Ca to balance them).
> And feeding when the plant (roots) is inactive could throw leaf nutrient levels out of balance as well.
> I think I read Ca. foliar apps. did enter the leaf somewhat but was totally imoblie so of little benefit.
> ...



Yup the whole K lite strategy always included an increase in Ca/Mg availabilty. I agree it takes roots to do a good job with Ca uptake, but I think in several rootless cases I played with, if you plant in moss and give a dose of kelp, then even the new root nubs will help you out. If the plant went rootless because of low K, then expect the lower leaves to shed as the stem starts to push out. But because the plant will have low Ca this is the most dangerous time to expect an Erwinia outbreak too as the plant lyses off old leaves to let new growth start.


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## Rick (Jul 25, 2012)

The secondary aspect of calcium hydroxide use with Urea goes with form of nitrogen.

You need higher alkalinity (from the hydroxides) to plants to utilize ammonia from urea.


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## ChrisFL (Oct 2, 2012)

Bumping this thread, 

Since the summer, I have been downpouring my main tank between 3 and 5 PM. I changed nothing else. Things are still soaked at night when the lights go off and the computer drops the temp to the low 70s/high 60s. My daytime temps are 86-88 on the warm side of the tank, and 79-82 on the intermediate side. Plants that have been stagnant in growth have suddenly begun to break eyes open and make new leads. I have observed zero rot and haven't lost a single plant.


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## nikv (Oct 2, 2012)

I haven't read this entire thread; only the first page and the last few posts. I always thought that the "don't water late in the day" rule applied only to those plants that had crowns that would trap the water. I happen to water in the morning to mid-day simply because of my schedule. Sometimes an additional watering in the evening if it's a hot summer night.


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## ChrisFL (Oct 2, 2012)

Also, I continue to use zero fertilizer. None. Nil.


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## likespaphs (Oct 2, 2012)

as long as the air circulation is good and the temps are okay, i've come to the conclusion that it doesn't matter when one waters


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## Ozpaph (Oct 3, 2012)

People don't catch a cold (virus) because its cold and plants don't rot just because you water late it the day. But it is true that damaged, wet tissue would be more likely to become infected than dry, healthy tissue. Its probably more about air circulation and fast growing plants being more resistant to fungal attack.


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## ChrisFL (Sep 20, 2017)

Who wants to play some more in this thread?


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## Happypaphy7 (Sep 22, 2017)

What I was about to say is similar to what Ozpaph said above.
I usually water during the day, preferably mornings, but I also water at night.
I don't think it matters, really.
During the hot months, the rain usually falls in the early afternoon and then clears up. 
It can also go one for days and night. 
Rain doesn't really have schedules. 
Also, early morning dews drench plants on a daily basis in general.

So...I would say "water at night is no no" is one of those unbased rumors that float around in the hobby.

"Don't wet the leaves or you'll get disease spots" is another common one.
I wet the leaves on many plants and almost everything is fine.
Certain Oncidiums and Dendrobiums I had in the past, never got wet but they were the only ones that got disease spots. 
Probably didn't get cleaned by water enough. lol


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