Coffee is acidic, but most studies I've seen have shown the grounds to be pretty close to neutral. Somebody posted one on GW recently that showed them to be a little acidic, but all the others have put them very close to neutral.

If you're concerned about acidity, you can compost them first.

Thank you I found out the information

Here is a link that might be useful: Using Coffee Grounds Correctly

That article lists the pH of the grounds much lower than any other I've seen. Most of what I've read has put the pH between 6.8 and 7.2, or very close to neutral. The most acidic I've seen before this was 6.2.

This article said that 5.1 was the least acidic (actually most gentle) they'd seen.

I wish I believed they were that acidic, because my soil is alkaline, and that would help greatly.

They recommend adding lime to the grounds before composting the, but I think that's completely unnecessary, even if the grounds are as acidic as they say. Compost tends to turn out close to neutral even if acidic ingredients are used to make it.

Well I would use it if I lived in Utah. But where I live the soil is extremely acidic from the rain and just naturally. So I think I will stop using it pure mix it with more alkaline things like eggshells I guess.

The article is full of baloney. I tested the pH of coffee grounds myself a couple years ago because all the 'debate' I was seeing had me curious.

They were around 6.8 after brewing. I have not tested, but heard from someone else that the Starbucks grounds they tested were 6.2. Naturally, some variation in the grounds is to be expected. How well brewed they were would be a factor, possibly the beans themselves would be.

I have no idea how the person consulted in the article got Anyone who has reason to care what the pH of the grounds they have available can test the pH themselves with litmus paper. Then you know.

One of the nice things about coffee grounds is that the acidity leeches out of them into water so readily. One trick to growing acid loving plants in non acid soil is to acidify the water they are given. A thin layer of coffee grounds around the root area, replaced regularly will result in at least some acidification of irrigation water. A little vinegar added to the water does the same thing and it is a 'trick' blueberry growers exploit. They actually use sulfuric acid as it is stronger and can be mixed further, but the idea is the same. Forget the soil and acidify the water. Plants don't actually get anything from soil, they get everything from a watery layer around their roots. One can manipulate that watery layer by modifying the soil (because water filters through the soil), or go directly to the water itself.

Thanks, Justaguy. I've left this thread for a while because I didn't want my bias to taint the responses I gave, but what you posted is in agreement with everything I've read. Coffee grounds aren't acidic (dang!).

Even if coffee grounds are around 5.1 pH how much you add to your soil will determine what happens with that soil. To make a signficant enough change in your soils pH to affect plant growth you would need to add a lot of coffee grounds, probably hundreds of pounds. Adding the daily grounds from your coffee pot, probably about 3/8 teaspoon, is not going to make enough difference to affect anything.
Also since worms really like coffee grounds and do not like any thing far out of the 6.0 to 7.0 pH range that should tell any resonably inteligent person that the pH of coffee grounds cannot be far from that range and most certainly not down in the 5 range.

That's the problem with many "experts". They are very confident in the dogma that they have always propagated (heck- they're considered "experts"!)

"Adding the daily grounds from your coffee pot, probably about 3/8 teaspoon"

I can see we like our coffee at different strengths. :)

Actually, I've added a couple of hundred pounds of coffee to my lawn. Although my soil is technically more acidic than it was, that's a bit misleading. It would be more accurate to call it less alkaline. The more organic matter I add to it, the closer it gets to neutral.

these folks are right on Sarah - used grounds are not acidic, and organic material "attacked" by the usual microbial decomposers in your compost or soil that release the nutrients in a form useable by plants, neutralize things that are much off neutral either direction - aside from the fact that it's not the pH of the material applied that changes the soil pH, but the particular mineral composition - ie: sulpher or calcium

Bill

Actually its the number of free radical hydrogen ions that determine your soils pH. The more of them you gots the lower your soils pH.

If you want to get really technical- actually it's hydronium ion... which is a proton attached to a water...

My geek meter just went off the scale, folks ;-)

Use all the coffee grounds you wish, they aren't going to result in any large or long term pH shift.

There is nothing bad, or particularly special about them, just another waste item more useful in the lawn and gardens than the landfill.

"There is nothing bad, or particularly special about them, just another waste item more useful in the lawn and gardens than the landfill."
So how about 100 or so alkaloids that the plants concentrate in the beans to naturally ward off insects trying to predate on their way of propagating? These same alkaloids can be drawn in by plants to simulate the same effect. They may not alter the pH more than a half point towards the acid side, but they do serve a very important function.