Humidity Tray Evaporation Question

[temperance]

This has a high potential of sounding like an extremely dumb question, so prepare yourselves.

I bought this really nice humidity tray yesterday (at Birds Botanicals in KC, MO). The pots go on top of wood slats and there's an egg-crate-like plastic thing that goes in the main water reservoir. The nice lady at the store told me I don't need to keep it in there.

My question: Does a tray of water with stuff in it (pebbles, egg-crate thingy, etc.) evaporate better or a different rate than just a tray of water? In other words, when I see advice in orchid books about home-made humidity trays with pebbles and inverted saucers, do the pebbles serve a function *other* than support in keeping the plant above the water?

I didn't do too well in physics class . . .

[RenéeS]

From what I've heard, pebbles in the humidity tray create a bigger wet surface, so more evaporation can take place. If this isn't the case, I'll let other posters answer this

[Ross]

Been there, done that! The pebbles make a mess nearly impossible to clean and lead to spread of fungus, algae, etc. But more important is the fact that such a tray will do nothing to raise the humidity unless it is in an enclosed chamber. See this: Humidity near the bottom.

[Donald]

Golly Ross! I have copper trays with marble sized lava rock in them that have not seen fungus, algae or any other "demons" in the six years I've had them. I will admit that once a year the rock is washed but during the course it sits in the trays it has been not a problem.

[slipperfreak]

I do not believe that the pebbles will make any difference whatsoever in the amount of humidity the water creates as it evaporates, nor will it affect evaporation rate. The store-bought humidity trays are just "nicer" and sometimes easier to use/clean. Evaporation rate depends on the conditions in your home. In a warmer, drier house, you can expect the water to evaporate more quickly.

For the record, I used humidity trays my first couple years and found they didn't do anything to help me. The microclimate created by grouping your plants is more effective, in my opinion. A humidifier is also an option if your house is really dry; another thing I've used but have found it wasn't necessary personally.

[Donald]

I do agree slipperfreak. What I have going was done before any serious research on my part happened. The trays look great. I have a high end commercial digital hygrometer and the readings taken at the top of a six inch high pot versus a couple of inches above the trays
were near negligable. When I need humidity it's misting and "firing" up the humidifiers. Happy Holiday

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[nutgirl]

Temperance, that's one of the better introductions to a thread yet.
As others have said, there is no such thing as a dumb question. Questions are how we learn.

I agree with Donald. I have put my meter above the pot with and without the tray and there is very little difference. It's just too large a space to have any effect.
From the sounds of it, however, you will have a very cool looking orchid setup.

Regarding humidity, my plan is to fill the room with orchids. Any excuse for more purchases.

Maureen

[temperance]

Thank you! This has been very helpful. I especially like the advice to buy more.

Where I live, the air is extremely dry during the winter. My wife and I usually run two humidifiers during these months (and that's before the orchids -- and yes, we've added a third humidifier for the orchids). If we don't humidify, petting the cats or unfolding a blanket can cause big static shock, and it can really dry out one's skin. But it's still more mild than Chicago (where I lived for a number of years), so I'm definitely not complaining. I'm ... hmmm . ..what's the word I'm looking for?
thankful!

[Ray]

Joe and Donald - from a scientific standpoint, adding pebbles adds surface area, so has to increase the evaporation rate. Not that it's significant, mind you....trays are, as you stated, essentially worthless for boosting humidity.

Read the "humidity" article Ross provided the link to. It explains it pretty well.

[slipperfreak]

Originally Posted by Ray

Joe and Donald - from a scientific standpoint, adding pebbles adds surface area, so has to increase the evaporation rate. Not that it's significant, mind you....trays are, as you stated, essentially worthless for boosting humidity.

Read the "humidity" article Ross provided the link to. It explains it pretty well.

I probably should have phrased my response differently... The store-bought humidity trays that I have seen have bumps built in to the base, also increasing the surface area. So, unless the material makes a difference in evaporation rate (plastic vs. pebbles), then I would say there is little, if any difference between the two.

However, upon now re-reading the original question, I see that the tray temperance has has a removable insert in the bottom that likely has the same effect as pebbles. So I would say leave the insert in.

I apologize for any confusion that my lack of reading comprehension might have caused!