Mold in my S/H!!
 

Hi all,

I continue to fight the battle against a super dry cold winter in Michigan; the first try with S/H did not go so well since I put sad plants in there. So I am trying again with a healthy Oncidium Ornithorhynchum and a Paph. Raisin Pie "Hsinying" x Sib.

So far they are doing alright, with one little issue: the Prime Agra regularly grows a little dusting of mold on the top after I water. So far the plants do not seem to be suffering from it (the Oncidium has even sent up a new growth shoot!) but I am a little concerned as I killed another orchid by not paying attention to the mold.

The two plants are about a foot away from a semi-shaded south facing window, and the plastic pots rest on a humidity tray. I haven't yet had my min/max thermometer in here, but I suspect it gets to somewhere around 55-60 at night, and around 70 during the day (there's a heating vent about two feet under the humidity tray).

Is a little mold a big problem? Is there something else I can do to try to prevent the mold? One idea I have is to bring in an oscillating fan and try to get more air circulation in here. Would this help out?

I would really appreciate any advice you guys have.

Emily :)

P.S.: right now I am on a once a week watering schedule, and I regularly fill the container all the way up to the top with water before letting it drain out until the bottom inch or so.

I'd bet it's not mold, but is a buildup of minerals, whether from the fertilizer, or from manufacturing residues.

Keep in mind that almost all of the evaporation is occurring from the top surface, so that's where the buildup will occur.

When they are produced, all brands of LECA are manufactured by adding solutions of "binders" to the dry clay, so it can ball up (like making tiny clay snowmen). The amount- and types used is how the porosity is controlled, but the binder minerals may not be completely removed during firing.

Secondly, they usually quench the pellets when the exit the kiln, and who knows what's in the water used for that.

So... before using the medium, it's wise to soak it for a while to help extract those residues. I add calcium nitrate and Epsom Salts to the soaking solution to accelerate the process, but it's not essential.

On the assumption that the plants are established now, I would suggest watering more frequently for a while to flush the minerals away.

Hi Ray,

Thanks for this. I have checked, and there's some mineral buildup as well, but this is definitely a fuzzy mold. I'm going a little light on the watering because I just transplanted them last week. Luckily, there is not a lot of mold, but it's definitely there. Do you think that maybe the plants are not warm enough? I had thought that might be part of the problem; or, maybe they are not getting enough air circulation.

Emily

I based my speculation, above, on my own observation, and yeah, the mineral growth did appear to be fuzzy, but you're looking at it directly, I'm not.

One thing that I think is correct is the mold will primarily only grow on decomposing organic matter, and should not be a factor on the clay.

Warmth is probably a good idea, too.

If it truly is mold, won't a spray of Physan 20 tame that down?

Oh, I didn't know that the mineral growth could be fuzzy. That is a good thing to know. I will go home and check it out again.

I will also check out the Physan, so that if it is mold I can just nail it that way.

Thank you so much Ray and Ross!

Don't use Physan 20 "just for kicks". If you have a magnifying lens, try looking at that "mold" through the lens and see if you can detect crystalline structure.

It may be a transatlantic thing but when talking about mould (english spelling for mold!), are we talking about true mould i.e. musty odour growth which appears when something has died and the mould is breaking it down or are we talking about algal growth which would appear on constantly wet s/h pellets and as far as I know is only unsightly (ruining the look of our shiny wet pellets), but harmless ?
Algal growth would be a true dark green, mould tends to be grey (more english spelling....for gray!) greyish green or brown etc.
Just an idea before you may go unnecessarily reaching for the Physan?

Pals

I am having a similar occurance with my terra cotta pots. I have noticed a white line of what appears to be mildew starting at the base of several of my pots and spreading upwards. I can completely wipe it off with a damp cloth but it will be back in a week or so.

Ah, now we're talking colours (colors!) so we can almost see what we're talking about without photos!
The white line is more than likely to be calcium/mineral deposits because you water with tap (fawcet!) water which is hard?
(Okay, so I'll stop with the english translation, it's beginning to annoy me too!)
Do some of your leaves have a slight, hardly noticeable white edge to them, particularly those you've had a while? This is also from mains water spray, running and remaining on the tips of the leaves, evaporating and building up a fine deposit after time.
It's said that this long term hard water does no good for orchids because it clings to the roots preventing them to function properly.
I suppose a test would be to select your newest orchid (with no white line) and only water that one with rain or distilled water, see what happens. No white line, it's your water - white line, it's probably the pot!
So don't worry Oldguypops, you're NOT going mouldy just yet!

Pals

Actually, I don't have hard water. I use Detroit city water which is quite good (100 ppm) after I let it sit for a couple days. And I guess the growth isn't white, it's more like light gray.

Do you still think it might be calcium?

Hello again Chris!
Only 100 ppm?, that's very good, enviable even, I don't think you'll have many worries with calcium.
Have attached a photo of one of my terra cotta-pots, the markings are a familiar sight to everyone, even patio pots get the same marks.
My water is hard, you can see there is algal growth at the base where most of the water collects inside after watering, I've attached the photo regarding the original post and to identify whether the green algal growth is the "mold" we are talking about on s/h pellets. The "white line" is a different matter and as it always appears above the algal waterline, I believe this is not mold but a "scum" of various contaminants sitting on top of the waterline and being absorbed through the porous sides of the pot over time (think about the ring around a bath if you hadn't washed for a month!) or a harmless reaction to water from the pot itself, even soft mains water contains some chemicals.
Unless its a pointer to something like calcium which could cause a problem, (and we know it probably isn't in your case), then I wouldn't lose any sleep over it.
100 ppm eh? hmmmm.....that's worth considering a move to Detroit!

Pals

Yep, those are obvious calcium lines.
Mine are not like that. I'll get a pic on later tonight.

Thanks

That white line you have can be a build up of salts . So you might have to use less fertilizer. I fertilize every time I water , but at a lower rate this seems to help/

I was 95% sure they were calcium marks but I deal with my problems by going into a total state of denial......that is until some-one brings me back to reality....thanks a lot Chris ;) !
If you're not putting anything nasty in (unlike me - calcium), then I can't see why anything nasty should be coming out but yes please, pictures are always interesting!

Pals

Many thanks for your view Des, but I'm sure it's not salts from fertiliser, people talk about fertilising their orchids weakly weekly or every other week or even monthly.
I can talk about fertilising mine in six month stints minimum (yes, my head is hung in shame as it should be :blushing: ) which makes me believe it's just a manifestation of whatever goes into the pot, harmless or harmful. Water may go in sparkling clean but think what that media must be like after 6 months or 1 year!

Pals

Just a thought, some years ago I bought some hand made clay pots to plant miltoniopsis , the plants took an instant dislike to these pots and i soon noticed a white powder covering the outside of the pot. It turned out that the person making these pots mined the clay from a dry river bed very close to a salt works !!!. So your problem could be the pot!

Here are some pictures of what I have on my pots. As you can see in the third picture, I am able to wipe it off with my finger.
It sure looks like mildew or mold to me. :yikes:

Any thoughts?? :hmm

I have a similar thing happening to a certain set of pots I bought. When kept constantly moist, these pots develop the whitish stuff on it, and sometimes it turns green as well. It also doesn't smell too great. I have a feeling it's to do with the pot - I think some pots when fired are done so a certain way, or perhaps there is something put into the clay to discourage algal/mold/mildew whatever growth. Pots that don't get the treatment end up looking like this. I water all my plants the same way, and fertilize the same way, and yet only the plants in one particular set of pots gets this affliction.

Morning Guys!

These marks could be caused by a number of things but without an in-depth labratory analysis, I guess we'll never really know exactly what it is and although I didn't agree with Des' fertiliser suggestion I still strongly believe he, (like Calvin) is right in that its a chemical reaction not an organic one (mold).
I suppose in the final analysis, our plants can give us enough problems without looking for them, those marks have been around for as long as terra cotta pots have. The plant will tell you if something is wrong, until then why look for problems which may not exist.
I found a couple of articles, extracts reproduced below (hope I don't get nabbed for copyright!), one is from a professional potter, the other a University horticultural lecturer:

"Earthenware pots are quite porus, and, in addition, if they are from an Asiatic source the clay may not have been properly washed/prepared and may contain various salts that may react with your plants as they leach out from watering, especially if the water you are using is rainwater,which tends to be mildly acidic! (Similar to efflorescence you get on some brickwork, it looks like a white powdery coating)!"

"Unglazed clay containers are popular, but can be heavy and also tend to accumulate unsightly salt residue as water evaporates from the surface. This residue is generally not harmful to the plant, unless it accumulates in the soil"

Unfortunately the second extract doesn't hint where the salt residue originates from, the water or the pot and although they may or may not have the answer, both suggest it is still a chemical rather than organic reaction.

I suppose you could always move your collection over to plastic pots Chris? ;)

Pals

Thanks for the research Pals.

I put all of my orchids in the clay because I am a "waterer", but I have just ordered some clear plastic replacements. I will eventually repot everything into the plastic, and will, I believe, solve the problem.

After closer inspection last night, I noticed that it happened on 3/4 of my pots, but not all, lending credence to the "poor clay" theory. The more expensive clay 'orchid' pots are clean.

Thanks to all who responded.

IF that's the solution Chris........you're welcome!
Hope you haven't got toooo many orchids to move over to plastic, that could be a task?
Feeling slightly guilty that we may have hi-jacked Emily's original green? mold topic on top of S/H pellets and turned it into a white line on base of pot topic!
Sorry Emily!!!!, hope you get an answer too!

Pals

:hijacked: Yes, Sorry for the Hijak Emily, although, our problems might be the same. Your mold/mildew is on the clay also from the sound of it, but yours is in the medium where mine is on the outside.
I hope you received a good answer as well.
:goodluck: