Water in morning vs. evening >60F

[tropterrarium]

Watering at night is an issue with Botrytus below around 58F night time temperature, so during the colder periods morning watering is certainly indicated.
But what about the warmer seasons when night time is >60F? Is there an advantage to watering in the evening?
My way of thinking has been, that by watering in morning, the evaporative cooling will help keep peak temperatures in check [I do have "under bench" misters, foggers, and swamp cooler; all with automatic controllers]. An other way of looking at it is that there is longer time for plants to absorb water if watering is during evening.
Both arguments make sense, so either I am missing something, or it does not matter. Anybody with some reasoned opinions?

I grow mainly mounted (70-80%) in pretty good humidity (RH60-80%: without watering), in a small GH and two terraria.

[RJSquirrel]

Stomata close at night (or in the dark) as a plant only transpires during the day (or in light) and stomata are part of the transpiration process. if you water them at night the water will still be there in the morning bec the stomates have been closed and no transpiration has occurred. Thats why we are told to water during the mornings is to take full advantage of the water with the light.

[lambelkip]

you have that backwards. the stomata close during the day, and are open at night. the recommendation to water in the mornings is to reduce the possibility of a Botrytis (or other mold) infection, since these types of mold grow best when it is dark & damp.

In summer, I water both in the morning and at night, because of the extremely low humidity here. If you're keeping the humidity between 60-80%, you probably do not need to water more than once per day (if that much). of course, this will vary depending on what types of orchids you are growing.

[Bud]

I am with RJ about this....sunlight, is a key reactant in photosynthesis. Most plants require the stomata to be open during daytime....the air spaces in the leaf are saturated with water vapor, which exits the leaf through the stomata (this is known as transpiration). Therefore, plants gain carbon dioxide by simultaneously losing water vapor; and you need the sun's light and energy to do that.

yet Kip is right in saying that watering at night might attract bacteria and sickness to the plant

[RJSquirrel]

backwards hey? Im dissappointed with you kip. your reading comprehension of scientific facts needs improvement

[Ray]

In CAM plants (some, but not all orchids), the stomata are only open at night, as that is when the relative humidity is naturally higher. It is an evolutionary adaptation intended to conserve water.


Ray Barkalow
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[orchidsarefun]

This is a good question. We had a speaker at our local Orchid Society who remarked on the fact that in Thailand, it rained day and night and that the plants, in a natural setting and in grow-"shelters" were fine. The only difference to the growing conditions here, that he could come up with as perhaps an explanation, was that here grow and green houses are enclosed. So, maybe, if there was strong ventilation or air movement, plants could be watered at night ? We would have to hear from people who have watered regularly at night; probably few and far between as everyone is always "told" to water in the day, and as early as possible.

[lambelkip]

Originally Posted by Ray

In CAM plants (some, but not all orchids), the stomata are only open at night, as that is when the relative humidity is naturally higher. It is an evolutionary adaptation intended to conserve water.


Ray Barkalow
Sent using Tapatalk

My mistake, I thought most orchids were CAM.

Every orchid book I've read that recommended watering in the morning explained that it was to prevent rot.

However, I've never heard of any scientific study showing any benefit to either watering time. If you're willing to try it out, and it works for you, let us know.

[gnathaniel]

Originally Posted by lambelkip

My mistake, I thought most orchids were CAM.

Every orchid book I've read that recommended watering in the morning explained that it was to prevent rot.

However, I've never heard of any scientific study showing any benefit to either watering time. If you're willing to try it out, and it works for you, let us know.

I think you're more right than not, Kip... From what I've read it's estimated that at least 60% of all orchid species use CAM to some extent, and AFAICT most though not all of the commonly-cultivated species/hybrids fall into this group: Laeliinae, Vandeae (incl. Phals, Angraecoids, etc.), many Pleurothallids, many or most Dendrobes/Erias/Bulbos, and many or most Oncidiinae/Maxillareae. Most epiphytes or lithophytes of any genus experience enough moisture variation throughout the year that they've evolved capacity for facultative and/or 'weak', if not necessarily obligate 'strong' CAM.

Besides, even if an orchid is an obligate C3-metabolizer doesn't mean it closes all stomata at night; not all C3 plants exhibit complete stomatal closure at all times. Most plants vary stomatal opening and closing in response to environmental conditions beyond just day/night. Also, many CAM-users are facultative, using water-efficient CAM as needed and the more energetically-efficient C3 as daily or seasonal conditions allow. I found a recent paper describing an Oncidium (previously considered obligate C3) in which the roots and pseudobulbs, though not the leaves, switched to CAM when drought-stressed. So actual plant metabolic strategies are a lot more variable than just C3="stomata open during the day" and CAM="stomata open at night", but regardless I can't agree with RJ's contention about diurnal stomatal cycles, especially WRT orchids more of which can use CAM than can't...

tl;dr--most orchids we grow are unlikely to have all stomata closed at night

[gladwrap]

Hello I am a newbie to this forum, this is the first post but I am confused already,do you water day or night,I have aussie natives and have always watered before lunch so they are dry before dark especially cold wet nights

Please go easy on me.