Let's talk mold again

At about this time last year I posted about mold. 

Let's talk about it again today, but from a slightly different angle.

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In the photo above you can clearly see the outline of where a sheet of cardboard had been left for a few weeks. The sheet was dry for most of the time but did get a soaking recently (which is when I moved it to the compost pile).

See how the concrete that was protected by the cardboard is cleaner than the surrounding parts? I'm thinking that this darkening is due to mold, not to soil or other dirt. 

Here's another example:

The places where several nursery pots were kept are cleaner than the surroundings again. Surely if this were just dirt then the leaking soil from the nursery pot drainage holes would have stained the ground -- but you can see that's not the case!

I was also thinking that perhaps this is due to tannins from fallen leaves -- they could darken the driveway easily. But then I remembered my blower-obsessed neighbor who has the cleanest driveway on the street -- she power washed the driveway during the summer and remarked at how dirty it gets every year. I assume she was talking about this darkening from mold.

Want to see more evidence? Look no further than the deck:

The composite boards are notorious for getting those dark mold spots. I power washed the deck at the start of summer, so this is at most four months of buildup. Blech.

What's interesting to me is that protected spots -- like under the covered grill, or closer to the house (under the eaves)...

...show much less darkening and no spotting. (In that photo, the closer to the bottom of the image the closer to the house). We had a period of many weeks with no rain this summer, and that didn't stop the deck mold from forming -- it can't be dryness that keeps those areas relatively clean, can it?

So I have to conclude that the mold spores are falling from the skies, or are at least in the air that's circulating everywhere. Is that the right conclusion?

Just like last year, the St. Louis region is a hotspot of mold spore activity right now:

The count certainly goes up when the leaves fall and they get a bit of rain on them:

Thanks autumn -- my allergies thank you too!

(I really should check the mold spore count map at different times of the year. I'm sure that it's high in the spring and summer too, but I never check until fall...)

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