We have great moss growing between and on the bricks on a patio on the north side of our house. It always seems to do well. This fall I slipped on what I thought was mud, but actually appears to be rotting moss - it's like a dark brown, slippery, slime:

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It has been happening for the past few weeks, starting before the leaves on the trees started to fall.

Any idea what's going on?

  • If you don't mind my train of thought... Do you have a decent microscope? I'd look at a sample, and see if I can find and identify possible pathogens. there should be some concentration, if this is a disease. – J. Musser Oct 20 '14 at 22:26
  • Good idea. I might be able to borrow one. – That Idiot Oct 20 '14 at 22:28
  • And if you find what could be a possibility, and are having trouble, the gang over at Biology beta will be happy to try their luck. – J. Musser Oct 20 '14 at 22:49
  • Wild. It looks like molasses, but I don't recommend you taste it. Are you sure someone didn't just pour something weird on it? Is it spreading or localized? Have you ruled out insect causes? Is it only by the cement? Fly ash in cement has heavy metals in it, I hear. How does it smell? – Brōtsyorfuzthrāx Oct 21 '14 at 0:04
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    Hunch is the technical term for a bunch after a long absence ;-) – That Idiot Oct 24 '14 at 1:49

It looks like slime mould and I'm pretty sure it is - it's possible for this to grow over and in moss if the area has been pretty wet for a while, the same way it can on lawns. You could try blasting the affected areas with a high pressure hose, or at least with the tap turned on full. If that doesn't work, what will work is mosskiller - which of course you don't want to use because it'll kill the moss too. On the other hand, it's pretty dangerous and slippy as it is. If you can bear to leave it, it should just pass.

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    Doesn't look like any slime mold I've ever seen. And even if it was, you could kill it with fungicide. – J. Musser Oct 22 '14 at 19:21

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