Constant humidity vs Constant Irrigation

[DirtyCoconuts]

for catasetum, i grow mine in a pot that sits in a large, deep saucer of water. the media in the pot is an inorganic mix.

they do very well

if they go dormant, i remove the saucer and replace it when the new growths are of size to require water.


so constant water. but only in my yard and on this genus.


also, for other genus like buolbophyllum, they will hate you if you are letting the roots dry out at all between waterings. similar for oncidiums but very different for cattleyas. Dendrobium can take it unless they are latouria types or nobiles and then they have very different needs

you are asking about one of two choices for 132,000+ species care. it is too broad of a question in my view

[katsucats]

I'm admittedly not a great grower so I can't tell you the ideal environment from a practical perspective, but I like thinking about theory. And theoretically if you were to subject an orchid to constantly high relative humidity , it wouldn't be able to dry off, so you would also need good air movement to prevent other problems like mold (learned this the hard way with some hydroponics buckets). But aside from that, I guess the question is whether high relative humidity is the same as constantly watering? Would 100% RH be equivalent to submerging the plant in water, with air movement analogous to water oxygenation in the latter?

I would imagine that watering can vary by the size of water droplets. On one extreme, we dump buckets of water, then most of that water drains somewhere. Very precisely, I would think that the only water that matters at any given time is the water in direct contact with the plant. So on the other extreme we could use a very fine mist, and if applied evenly and densely enough, it should provide the same water contact with the plant as dumping water. Following my logic, if the mist is very, very fine, then the evenness of the application should approximate humidity in the area in close proximity to the plant. Putting aside the practicality of constantly spraying fine mists, would this be incorrect?

Further, if theoretically tuning humidity is similar to tuning irrigation frequency, then the only real question is which is more practical. For instance, for plants that require a bit of drying, it would be hard to cycle the humidity quickly as opposed to watering, then draining. For plants that require some constant wetness, then high humidity might supply it, if my reasoning is correct, but also carefully planned media selection and arrangement. Humidity would be more stable, but less flexible. With irrigation tuning, we can graduate the moisture i.e. with S/H, or putting moss in certain parts, or using bigger or smaller pots, etc., whereas the only way to do this with humidity is to design an enclosure and place humidifiers and exhausts strategically.

So I think if budget and room comfort are not issues, then it might be a sensible policy in general to set the humidity as the baseline level that all your plants could tolerate even when they're supposed to be "dry", and then fine tune the rest with irrigation, to minimize water maintenance and at the same time maximum flexibility. This conclusion ended up being very intuitive and obvious. If you're only growing Bulbophyllum in the room, it might make life easier to set a high constant humidity. If you're growing Cattleya, then maybe lower humidity to allow roots to quickly dry in between waterings. But if it's practical, maybe disregard humidity and use an aeroponics mister or NFT system to constantly water for example.

[Ray]

Originally Posted by katsucats

Would 100% RH be equivalent to submerging the plant in water, with air movement analogous to water oxygenation in the latter?

No, because at 100% RH, the air is holding the maximum amount of water it can, but it's still a vapor, not a liquid.

[katsucats]

Originally Posted by Ray

No, because at 100% RH, the air is holding the maximum amount of water it can, but it's still a vapor, not a liquid.

On a molecular level, the difference between vapor and liquid is just the density of the molecules. So perhaps it would be more accurate to say 100% RH is analogous to highly oxygenated water or high frequency (on-off) watering?

[estación seca]

It's easy to forget relative humidity is relative to temperature. 100% doesn't mean the air is all water vapor. It means no more water vapor can be in the air. Evaporation from medium or transpiration from plants may still occur because some water vapor condenses on surfaces and is removed from the air, leaving room for more evaporation.

[Cach26]

Everyone is right, it's a very broad question, so let's focus on water voracious plants in their active stage (Catasetums, Anguloas, Lycastes, Phrags?)

I agree that, although environmental humidity is important for prevent pest problems and aid overall plant health, a hobby grower does not have the resources to have a greenhouse with humidifiers or equipment to raise or lower temperatures

"Getting big pseudobulbs starts with genetics. You can't get a Chihuahua to grow to Great Dane size by feeding it more."

Still, here's a good example of how a "Chihuahua becomes a Great Dane"

Well... the web does not allow attaching the link of the video on youtube, whatever, it's called

"Cultivo de Orquídeas Anguloa | Alma del Bosque"


See from minute 18:30

According to the grower, it developed like this because “they poured a really good AMOUNT of water on it.... On the roof where I had the plant, there was a hole in the plastic, and when it rained it dripped on top of it”

That is why I am doing a test with my Anguloa Uniflora, using drip irrigation. Drip irrigation 8 hours a day, 1 drop every 20 seconds, and I remove it at sunset, let's see what results it gives me.....

With a medium substrate half bark, half inert material. I water deeply 2 times a week. Ambient temperature from 25 Centigrade to 30 Centigrade

[katsucats]

Originally Posted by Cach26

That is why I am doing a test with my Anguloa Uniflora, using drip irrigation. Drip irrigation 8 hours a day, 1 drop every 20 seconds, and I remove it at sunset, let's see what results it gives me.....

With a medium substrate half bark, half inert material. I water deeply 2 times a week. Ambient temperature from 25 Centigrade to 30 Centigrade

I am building an area outside that uses a 1/2" pipe to drip misting spray nozzles, connected to a timer. The original plan was to use drip to save water and maximize the number of plants in a zone, but I have a question/concern about this. In loam/clay soil, drip works because saturated soil allows excess water to be absorbed horizontally over a wider area. However, in orchid media with medium bark or LECA that allows water to flow through faster than sand, the water may never spread more than a couple centimeters horizontally, so the roots besides the point where the drip is installed wouldn't get water. At least that's the way I envision it in theory. Please report back after your experiment and let me know if I'm wrong.

Perhaps drip might work with a semihydro setup, over a mount with moss, into clay jars/ollas that disseminate water into a larger area, or a gravity-based reservoir system that releases water when it's filled up enough (I'm thinking something like the sozu with a gallon jug on one end).

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[Ray]

Originally Posted by katsucats

<snip>I have a question/concern about this. In loam/clay soil, drip works because saturated soil allows excess water to be absorbed horizontally over a wider area. However, in orchid media with medium bark or LECA that allows water to flow through faster than sand, the water may never spread more than a couple centimeters horizontally, so the roots besides the point where the drip is installed wouldn't get water. At least that's the way I envision it in theory.

All media will spread the water horizontally. The issues are the rate at which is does so, and the evaporative forces of your environment working against that.

If the water is dripping on a single media particle, it will eventually become saturated and will start to share water with the particles making contact with it. As they become saturated, they will do the same.

LECA wicks really well, so will probably be a better choice for such a setup. Besides, having an automated watering setup is bound to bring out a bit of laziness, and it may be too late before you notice that constantly-moist bark (or other organic components) has decomposed and damaged the roots.