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.