Q&A – What is this slime growing on my gravel driveway?

“There’s some type of slime
or fungus growing on my “limestone driveway. I was hoping you could “tell me what it might be,
and what causes it. “It is dry most of the time,
but when it rains it swells up “and turns a dark greenish
color, and is slimy. “It is also spreading. I don’t know how to treat it because I don’t know
what it is.” And this is from Melanie. Have any idea what that is? – Looks like some
type of slime mold. – It’s a type of algae. – Type of algae? Ok. – Type of algae. – So all the wet weather
that we’ve had– – All the wet weather. – is the reason you have it, and
it’s going to go away when we get into the summertime. – Once it dries up pretty good,
Nostock is what it’s called. Nostock. – Nostock. – Nostock. Some people
actually know it by, they call it witches butter,
or star jelly. – Is it edible? – I don’t know if I would eat that. – I mean, seaweed is algae– – Yeah, I don’t
know if I would eat that. [laughs]
– and it’s edible. Alright. It really doesn’t
look that tasty, does it? – No, it doesn’t
look that tasty too me. Yeah it’s green and slimy. And of course the rain
actually rehydrates it. But I usually see it in lawn
conditions when you have compact soils and poor drainage. – hmm. Well it likes the moisture. – Likes the moisture. So it will dry up,
but then once it rains, rehydrates. – So you need to improve your
soil drainage in your lawn. – Aerate. – Aerate, right. – You want to go another
route, belive it or not, of course there’s a fungicide
that controls algae and moss. It contains what,
potassium salts, the fatty acids. You can use one of those. Hook it onto the end of
a hose, spray it out. – Yep. There’s some things
that you can use in ponds. – Ok. – That control, algaecides. And that would
probably do the trick too. – Ok. So yeah Melanie, Nostock. – Nostock algae. – So it’s not a slime
mold, it just looks slimy. – Yeah, cyanobacteria is what
we learned at school that it also goes by, yeah. Slimy. I don’t know if I
want to eat that though. – Yeah.


  1. There’s 2 (easy) ways to get rid of it: the expensive way is with the herbicide called Scythe which only comes in 2.5 gallon containers and costs about $180 US dollars.

    The cheaper way is with a weed torch. These are anywhere from about $40-$60 depending on where you buy them. Amazon sells them. You attach them to a propane tank. I am
    not talking about the small ones, you need one which has a soda-can sized “barrel” at the end.
    When the nostoc is dry, go out and burn it up with the weed torch. Make sure you get all of it and make sure it burns thoroughly.

    There are other herbicides which can control it, and possibly kill it; however, they will take several (maybe even many) applications, and they are not guaranteed.

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