Humidity tray question

[skipper]

I bought a nice humidity tray from repotme.com. I have my Phals. on it now and they look great. I have not put any water in it yet. My question is what do all of you do with your trays? Do you have water in them all year long? I was not sure about the summer, and was only thinking about the other three seasons. Looking forward to all replys.

Dale

[Emma Grey]

Hi Dale,

I always keep water in mine (and by always I mean since I bought the trays several months ago - I'm an orchid newbie) because it's somewhat dry here and I want to make sure that my plants have some extra humidity. If your humidity is high enough during the summer I guess you wouldn't need to put water in the trays for that season, but I'm no expert.

[dounoharm]

i always let the water run thru the rocks on the humidity tray, but it drains out into a bucket on the floor, leaving the rocks well wet....i sometimes run water thru it twice a day....but it is terribly dry in that house, with a/c running constantly....

[ChryssM]

I use catch trays under ALL my plants unless they're outside !! Most are homemade using different size and type trays, some trays I found at Home Depot and others from microwave dinners ! I bought the plastic grid in 3 x 4 foot ? (I'm not sure, I cut them all a long ago) sheets at HD and cut them to fit each tray with diagonal cutters (dikes).

I try to keep water in them all the time and, contrary to some opinions, it DOES increase the local humidity around the plants. For almost all of my Bulbophyllums I've taken the grid off and every time I water I leave some standing in the dish.


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[orchids4me]

I use cat litter boxs in designer colors lol I try to get all one color but I line with 1/2 rounded what's called drain rock. I work at a rock quary so I can get like 200 pounds for a $1.54. I plan to change them over to how the member above me does theirs. The gravel si heavy and my poor 6 ft banquet table is bowing in the middle now from the weight the past year. You find those grids at home depot in the lighting section where the cfl ect fixtures are they are roughly close to $12.00 a sheet where I am. So slowly I will convert them over and use the gravel for drainage in out door plants or something lol

[ChryssM]

The rocks would be good for weighing down pots for outside. I put possible easy plastic pot knock downs in bigger clay pots and fill the surrounding space with rocks.

[1joyceh]

When aquarium gravel is on sale, I pick that up, mix with small rocks for the trays. I use them in the winter. Come spring, I use outside in landscaping, makes an interesting look, and in a few months, kind of "absorbed" into the planting beds, but, I think, increasing the drainage and may aerate the soil? Seems to work

[Ray]

Originally Posted by ChryssM

I try to keep water in them all the time and, contrary to some opinions, it DOES increase the local humidity around the plants.

I suppose it depends upon what you mean by "around". A few millimeters, maybe.

Another grower and professor in plant biology (who no longer participates in forums, I'm afraid) did an actual study a few years back, measuring the humidity around plants on trays versus those not, and he measured absolutely no difference in the "local humidity".

From a purely scientific basis, his findings make sense:

• The amount of evaporation from a tray or pebbles in a tray is minimal. More on that later.
• The forces of nature want to spread that tiny bit of water vapor uniformly throughout the air volume in the room.
• If you have fans running (a really good idea) that will happen even faster.
• Unless your growing space is sealed off from the rest of the house (and world, in fact), that humidity is going to spread there, too.

I say "minimal" evaporation based upon the following:

Let's say we have a 10' x 10' x 10' "room" (size selected for calculation purposes). At 74°F (also selected for math simplicity), that volume of air can hold one-half pound of water to give 50% RH. One-half pound of water is about a cup in volume.

If I have that water in a coffee cup, it has a surface area of about 7 square inches, and it will sit there for what? - a week?, more? - before it is all evaporated. Pour it into a tray and we increase that to about 250 square inches, adding pebbles maybe doubles that, but it is still not a significant area for evaporation, so it will still take days to completely evaporate.

If you want a significant increase in humidity, you need to heat the water or increase the surface area a great deal more than that. Since we don't typically heat "humidity trays", let's focus on increasing the surface area:

A typical cool mist vaporizer puts out droplets averaging about 40 microns (0.04mm or 0.0016 inches) in diameter. At that size, my cup of water would consist of over 7 billion droplets, having a combined surface area of over 55,000 square inches - more than 220 humidity trays. And even at that, sometimes it doesn't all evaporate, leaving a wet area. If 55000 square inches doesn't completely evaporate, how is 250 going to?

Don't forget that I'm ignoring air replacement in the room, which requires faster evaporation to sustain the %RH.

[ChryssM]

The amount of evaporation from a tray or pebbles in a tray is minimal.

Ray, don't get me wrong, I LOVE scientific studies but whatever word is used, like minimal, the water IS evaporated TOTALLY and CONSISTENTLY!

[Brooke]

The very unscientific test I did showed a 10% increase in the area of the pot/leaves. Two feet up, no there wasn't the 10% increase but around the leaf area, growing under lights, 10% raised my humidity to 50%.

If you want to raise the humidity by 20% fill the tray with warm water. Of course as the water cools down, it drops back.

Anyone with a humidity gauge can run the experiment to see if it does enough. I was only interested in raising the humidity in my plant area, not in the whole room.

Brooke

[11Orchid126]

Every once in a while in the trays I use water with an algaecide (from the aquarium store) in it to prevent the growth of the ugly green stuff.

[ChryssM]

It CAN get pretty thick if neglected ! I just scrub them out every once in a while if I see it's necessary.

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[skipper]

Thanks to everyone. I am going to fill the tray today and see what happens. Even if the rise in humidity is small, it will be helpful. Thanks again.

Dale

[cable]

I've never noticed much effect from humidity trays. And yes, I've measured the humidity above them: no clear difference. But if they are effective for you, use them! (The ultrasonic vaporizer things *are* quite effective, though.)

Using an enclosed space like a terrarium or orchidarium makes any humidity-raising device orders of magnitude more effective, if you have a place to put one. And you can have air movement inside it, too!

[ChryssM]

(The ultrasonic vaporizer things *are* quite effective, though.)

Only if you don't have water with a high mineral/salt content ! I traded mine in because it left a white powder over the entire first floor ! Had to wipe off my TV screen every few days !!! Didn't check to see what in our water would cause it to do that.

[Ray]

Originally Posted by ChryssM

Ray, don't get me wrong, I LOVE scientific studies but whatever word is used, like minimal, the water IS evaporated TOTALLY and CONSISTENTLY!

How quickly do they evaporate?

How large is the room they are in?

Is it open to other areas of your home?

Any open windows?

Any air movement?

I have no doubt that the water evaporates, but that doesn't mean it's truly enough to have a benefit to the plants.

[ChryssM]

How quickly do they evaporate?

How large is the room they are in?

Is it open to other areas of your home?

Any open windows?

Any air movement?

Right now I'd say 3 days.
Approx 12' x 15'.
Yes, another approx 15' x 20'.
No open windows.
Ceiling fan 24/7.

I see what you're saying but since I'm not a scientist I go by touchy-feely and it SEEMS to benefit them and the bottom line is that , if nothing else, the trays catch the water when I DON'T have time to take them to the sink and I just water them in place, infrequently. One more bottom line is that they are sitting on the plastic grids (except for my bulbs) and that allows air movement under the pots.

[skipper]

Chryss, I think you have a very good point about the pots sitting on the grids. The air can flow all around and under the pots as well. Some of the plastic pots have holes only on the bottom and these are blocked when the pot sits on a table. Also agree that the pots can drain alittle in the trays after watering. You don't have to put the pots on a small dish for this reason. Plus I think they look nice on the tray as well.

Dale

[janet_a]

i have a cheapie hygrometer on the windowseat where the majority of the plants are; in the winter, i keep water in the trays (pyrex baking dishes) and used to notice a slight increase in the humidity; however, at some point i reached a critical mass of plants and the humidity went way up (literally from <40% to a consistent 60%). so for one or two plants on a tray, i don't think it's going to make too much difference, but once you get a bunch of them in a small area respirating and aspirating at one another, the local humidity increases. if i forget to fill the trays and they dry out, it doesn't drop the humidity on the meter much.

but since the HVAC is a heat pump, and the entire house dries out, i try to keep as many bodies of water standing around as possible.

oh, and i shock the trays periodically with teaspoon per gallon bleach to keep the flora and fauna in the water under control.

(and the plants are on plastic coated wire racks that are set on top of the baking dishes so air circulates under them; fan on the plants 23/7.)

[ChryssM]

fan on the plants 23/7

Janet, is that a typo or do you really turn the fan off for 1 hour/day ?? Yes, I have also noticed that there's a lot more local humidity because they are all crowded together !!!

[janet_a]

nope, no typo; the fan shuts off around 7 pm, because i'm usually home by then and have turned the heat/AC back up, so i let the HVAC system do the circulating for a little bit. in the winter i have the fan go off around 7 am for an hour or so, then kick back in as i leave the house and turn the heat/AC down.

[Puddy1]

I notice that the humidity trays help for me. My plants are all grouped together on a table and I have noticed that, after watering, the humidity increases also. I also think keeping plants grouped together helps keep up the humidity.

[Ray]

Originally Posted by ChryssM

Right now I'd say 3 days.
Approx 12' x 15'.
Yes, another approx 15' x 20'.
No open windows.
Ceiling fan 24/7.

I see what you're saying but since I'm not a scientist I go by touchy-feely and it SEEMS to benefit them and the bottom line is that , if nothing else, the trays catch the water when I DON'T have time to take them to the sink and I just water them in place, infrequently. One more bottom line is that they are sitting on the plastic grids (except for my bulbs) and that allows air movement under the pots.

Chryss, it's all a matter of degree. Certainly the evaporation of the water indicates it is adding to the humidity, but is it enough to truly be of benefit? Let's do a non-scientific comparison to assess that.

If we assume the water starts at 1" deep, and it's a standard nursery tray, and it takes 3 days to fully evaporate, then you're dumping about a quart of water per day into the air. By contrast, standard room-size humidifiers typically put out from 1 to 15 gallons per day, with something in the neighborhood of 4 gallons/day - 16 times as much - being considered reasonable to sustain 50% RH in a standard room (whatever that means).

Add to that the size of your grow room, the size of the attached one, and the ceiling fan - all factors that reduce the "local" effectiveness - and you can understand why I don't think it adds much.

[NewGrower]

Would it make a difference if the plant is outside? All of mine are on my patio and the water evaporates pretty quickly out of their trays!

[janet_a]

being in florida is a natural humidity tray.

[ChryssM]

I guess I forgot to mention that my air washer/humidifier puts out 2 - 2.5 gallons/day into the growing room. Maybe that makes the difference by keeping the room humidity up so the trays DO affect the local humidity ?

[Stitz]

Originally Posted by ChryssM

I guess I forgot to mention that my air washer/humidifier puts out 2 - 2.5 gallons/day into the growing room. Maybe that makes the difference by keeping the room humidity up so the trays DO affect the local humidity ?

2 - 2.5 gallons/day is a significant quantity!! FAR more than the evaporation from your trays.

--Stitz--

[ChryssM]

I know, thanks Stitz !!!
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