It wouldn't be completely possible to tell without a specialist inspecting it. There are dozens, if not hundreds, of decay fungi that will happily grow in coffee grounds. Once used, they're damp, near-neutral in pH, rich in carbon, and darn tasty. If the fungus shows slightly greenish, it's probably trichoderma. Duluthinbloomz4 made the general statement: "Bluish-green to green molds are usually Penicillium or Aspergillus. Black to brown-black molds can be Aspergillus niger, Alternaria alternata, Cladosporium herbarum, Cladosporium sphaerospermum, or Stachybotrys chartarum (a highly toxic mold). Reddish or pink molds are usually species of Fusarium." It's a good guess overall, although there are plenty of other molds of those colors (as noted, green molds have at least three choices, and I'd choose trichoderma over the two mentioned). Or, why it's smart to clean the coffee maker occasionally... :-)

Thanks for the extra info, Alan. I actually am not extrapolating anything, myself. I just quoted someone who seems knowledgeable on the subject, and asked what others thought. I have no opinion on this issue one way or the other, but don't see any reason why I should use brewed coffee if there's any chance it retards growth. BTW, I used the phrase "concentrated" referring only to using the brewed coffee on container plants, where by the nature of the container itself, everything is concentrated. I didn't mean to imply that the liquid was necessarily concentrated. I appreciate what you are saying, but for me, I'll just continue using the used grounds in my compost, and not worry about saving the liquid. Actually, there is never any liquid to save. Only Mark drinks coffee, and he finishes his whole pot every morning. And I am the only one drinking tea, 1 cup at a time, and I finish those, too. So for us, the used grounds and leaves are the only thing we have to deal with. I don't know if Tapla has additional information on controlled studies on this or not, but it seems to me that would be the only way to get sound information. It would be hard to prove whether pouring coffee on a plant slows the growth of that plant or not, unless you have two plants in identical conditions, one getting coffee and one not. Then you could see which one grew faster. But I don't need to know that badly, and I suspect you don't either. As I say, if you are doing something that seems to work for you, why change? Me, if I want a tonic for my plants, I think I'll stick to proven formulas on the market rather than chance any retardation of growth. But I certainly don't expect everyone to feel the same way. I found an interesting thread on another forum, and shared it here. I have no idea personally of the truth behind either side of the issue. But my general rule of thumb in life is, when in doubt, use caution. So that's going to be my own approach. Marcia

@John, the idea of drying was only relevant to trying to get a better sense of the amounts involved (in more precise dry weight terms). Your garden doesn't care much whether it's wet or dry when applied. I would guess it is essentially impossible for a normally-sized household (like, less than a dozen people) to consume so much coffee for it to exceed the amounts identified above as 'too much' for anything but a small plot. And you'd notice because it would be well more than several inches thick. (I'm assuming that any coffee applied outdoors in air will degrade and lose any of the identified negative aspects over a period of a couple of months, because it's obvious. Most households could keep applying their used grounds forever, if the amounts are within reason). I should note, I'm being a bit lazy in terms of math. If you're worried I'm wrong in doing no math whatsoever, spread it out a bit more. Seriously, this is a silly thing to worry about (IMHO). Common sense.

That's great, Ingrid. I've just planted 5 new ones and I'm out there at least once a day seeing if anything's happening. So far nothing:( But the ones I planted 6 weeks ago are growing, especially a Bliss which got more sun. I got 2 and the other one has hardly grown at all. I made a mistake on the other thread about the amount the grower said to water. He said 20 litres (5 and a qtr gallons) 3 times a week, preferably by sprinkler (or drip) in the morning. He also has a video about planting new bare roots. I was amazed to see how short he recommends pruning them. He says they sell them with large top growth as that's what people want. He cut them to about 5".