Humidity tray question - Orchid Board

gardengirl13 · #1 02-23-2016, 11:37 AM

OK I'm not sure where to post this, so I'll post it here since the answers might help beginners looking for humidity solutions.

I have always used metal half sheet baking sheets with fish tank gravel for under my plants when growing them on the shelving unit. We moved and lived in a house for two years where I could just put the plants in three windows and they were fine. Not great humidity for them though. Now that we moved again last Aug none of the windows are good fro growing sadly. VERY sadly in fact. So I used the wire rack I had used in the past and put up some LED lights. All seemed to be going well until I noticed a weird white stuff in the trays. Not soft, more like massive hard water build-up. I tried to clean one, it washed off the rocks ok, but not the tray. I really had to scrub at it, but even before that I noticed something odd. The tray was beginning to get little pits and bumps where this build-up was!? What on earth is going on here? I twice used tap water, otherwise it's only been rain water since some of the plants have long roots that touch the water so I though it best to use what I use to water. This build up happened in the first month. I just originally thought it was coming from the very hard water. But nothing can build up THAT fast. Plus we had the water tested and it's only 6 grains, not hard enough to do that. Another weird trait to this white stuff, it climbs over the trays and flakes down. ???? I get a dust on the leaves below. What is going on here? I had the SAME setup in the other house and had it for over a year and this NEVER happened. I used tap water there and this house is right across the street from that one. Yes wells can be different. But I'm not sure they would be that different.

Some basics I think they're aluminum baking sheets plain not non-stick, like you'd get in a professional kitchen, they're way cheaper and what I use to cook with myself. The gravel wasn't rinsed first, which I'm thinking I should have done that, but can a small amt of dust do this?? Should I just buy new gravel and trays and try again and see if it happens? They're only like $10 compared to the plastic trays which aren't sized what I need and cost $40 each! I've looked into plastic trays to use instead and can't find anything like these. I really like the simplicity of them.

It's hard to see in this photo, but you can kind of see the discoloration and erosion/oxidizing whatever it is on the bottom left tray.

ETA: that was a shiny new tray

Orchid Whisperer · #2 02-23-2016, 12:35 PM

I don't know the size of your trays, but how do they compare to open-top plastic cat litter pans? $5 to $6 at places like Petsmart, maybe less elsewhere.

fishmom · #3 02-23-2016, 01:46 PM

I have an indoor grow-tent and I use trays in the bottom of it for humidity also. Between evaporation and drips from the fertilized plants, the deposits build up pretty quickly. I used a heavy foil tray once and it had pinholes in the bottom within days.

The best non-plastic solution I have found is old broiler pans from thrift stores. They have a spotted enamel coating that seems able to stand up to the chemical action. They are surprisingly hard to find, though. I don't know if there would be anything available in that finish that would fit your shelves.

gardengirl13 · #4 02-23-2016, 08:12 PM

The pans are about 13x18 I'd have to measure a litter pan. That might be a good option depending on how expensive they are.

As for the broiler pans I might actually have one or two that came with the house. I might have to look around! I also wonder if you can order them from the oven manufacturer?

Do you think it's mostly from the fertilizer? It has been dripped in there while moving stuff around and drips from the plants. I'm not sure why this didn't happen with the pans the last time?

Orchid Whisperer · #5 02-23-2016, 09:03 PM

Yes, I think plain aluminum would react badly to salts such as fertilizer. I think that's the cause of the corrosion.

Roberta · #6 02-24-2016, 01:57 AM

When I lived in a condo and used the spare bedroom as my "greenhouse" I used inexpensive plastic storage bins that I got from my local K-Mart or Target. Over the top, I used "egg crate", plastic light diffuser panels with an open grid (I think about 1/4") When I watered, the water had a place to collect, the plants were on a nice, stable base. Then, there is plenty of room for whatever water you use, you can water your plants well and have no worries about making a mess. I think this would accomplish the same thing as those "humidity trays" a lot more efficiently and trouble-free.

gardengirl13 · #7 02-24-2016, 10:13 AM

I was thinking of doing something like that, but the way I water I'm not sure it would work. This has also got me thinking that it might not be a great idea to let any fertilizers get into that humidity tray water in case it causes other issues not just corrosion.

Now what about the coated cookie sheets? Like non-stick. Will they not corrode? But how would the coating react to constant water? When I grew on windows I never had humidity trays obviously since the sills are so narrow and the plants did fine. But with the lights on a lot longer then the sun being on that side of the house where the windows were, plus in this new house we have forced hot air/AC in summer, I'm trying to help with humidity as much as I can. I do run a humidifier right in front of the shelving unit in winter as well.

Connie Star · #8 02-24-2016, 11:17 AM

I've used the plastic "humidity trays" which are really just drip trays, that you can get from orchid supply houses. The white stuff builds up on them too and is a devil to get off. I've tried vinegar without much success. The best way seems to be to just scrape off the white stuff with a dull knife or even a paint scraper. However, the white stuff did not harm the plastic. These trays are rather expensive. I also found "boot trays" that you can buy in the fall with gravel in them. They are kind of big and work best under deeper shelving. One thing you learn growing orchids is how to improvise!

gardengirl13 · #9 02-24-2016, 12:57 PM

Yeah I was thinking about boot trays since they're made to handle snow water and salts. Sizing is a bit weird though so I might have to look around a bit more. I don't really care about the build up too much. As long as i can scrape it off a bit and not let it build up to a massive amount. I'm more worried about the cookie sheets I'm currently using getting holes in them and leaking.

Baroness · #10 02-28-2016, 12:03 AM

I am new to this site but my guess, it is chemicals in the water. Same as when you boil water for humidity and the crystals in the bottom of the pan are the chemicals from the water. Best thing to do is either use spring water or just clean the pans weekly to keep the chemicals at a minumum.