Hi Lynn,

I'm delighted that you've asked this question. I love using coffee grounds in my garden. I find them extremely easy to use. They only fact you have to keep in mind is "Fresh coffee grounds are acidic. Used Coffee grounds are neutral"

Coffee grounds have a number of very practical garden uses. The general benefits/uses are:

- They are rich in nutrients (nitrogen, potassium, calcium, phosphorus, and magnesium)
- Worms love them.
- Slugs hate them (most but not all slugs )
- they smell heavenly
- They break down relatively quickly adding organic matter to your soil.
- They can be used as compost starter helping to heat up a compost pile.
- when densely packed they can form a crust with repels water. I created a 3" track at the back of my flower bed. It helps with weeds.

I use the "Sprinkle" method. Instead of dumping all the grounds under any one plant I sprinkle them around ( takes no time at all) You can sprinkle USED coffee grounds under plants and on your lawn. There's no hard and fast rule to how much. Common sense will guide you. If you notice any yellowing of leaves then sprinkle the grounds less often. Plants will quickly recover.

You can sprinkle FRESH grounds around acid loving plants, hydrangeas, lilies, etc. I used some old out of date coffee on my blueberry bushes.

I'm one of those people who happily ask for used coffee grounds from the local coffee shop. I have a normal compost bin and a big 3x3x3 ish worm compost bin. The worms go crazy for wet, used coffee grounds. They don't go near fresh grounds.

Hope this helps.

M

That's interesting, mirenda. Tell me more about using used grounds for slug control. They are attacking my new hosta regularly. Do I sprinkle the used grounds in a circle outside the hosta or throughout the hosta (on the ground, obviously)?

How long does it work effectively--like, how often would I need to re-new it? If it rains, does it need replacing? Anything else I should know?

Sorry, forum, that I digressed to hostas, but ragged hosta don't make an attractive setting for my roses, do they!

Who knows, I may expand and start using grounds on roses also. : )

Kate

Hiya Kate,

I've heard all kinds of mixed reports regarding slugs and coffee grounds. With Ireland's wet weather (very similar to the Pacific Northwest back home) the battle with slugs rages on.

In order to maintain my credibility i can only safely report two facts and tell you how I use them.

Fact #1. Slugs sprayed with caffeine solutions die however it takes more caffeine than is found in the average cup of coffee.

Fact #2. Using FRESH coffee grounds (sprinkled on top of soil) will deter slugs but not keep them completely at bay.

I use coffee grounds in conjunction with other measures. When I'm not being lazy I grind my eggshells in the food processor, mix equally with my USED coffee grounds and regularly toss on top of soil. This is an ongoing process.

My other measures? I've made my garden very hospitable to local wildlife. I regularly find lovely fat frogs in my garden on the hunt for juicy slugs (I don't live near a pond- I don't know where the frogs are coming from). I keep my garden teeming with worms, which attracts birds that eat slugs. I encourage my dog to eat them as well.

If you're not against chemical warfare, I usually do a massive slug pellet inch for two weeks in early spring, just as the slugs become active. It seems to cull them enough for nature to handle the rest. I'm working towards a chemical free garden but am not there yet.

To sum up, coffee grounds aren't the holy grail of slug prevention but they will help.

M

Hmmm--my response must be floating in cyberspace or something. Let me try again.

Thanks, Mirenda. Helpful information. I may just try to tough it out since the overcast, wet weather we are having in the midlands (USA) is rather unusual. Normally by July-August, semi-drought is the problem I have to confront. But with climate-change on the way, who knows--I may have to regularly contend with new growing conditions.

Kate

There is no problem with applying used coffee grounds at the soil surface, two or three cups at a time. It will cause the earthworm population to explode, just as alfalfa does. Six or eight cups of used coffee grounds provides enough nitrogen and phosphate for a season. The potassium is lost in the brew, but many garden soils have adequate potassium already.

Acidity is not the issue, rather caffeine is. Most of the caffeine is lost in the brew. In sufficient amounts, caffeine is toxic to plants, so be careful about applying unused grounds. Obviously, moist, unused grounds are most effective as a slug repellent because caffeine is what repels them.

Michaelg is correct. Acidity isn't an issue in USED coffee grounds. Be careful with unused (FRESH) grounds they are acidic. Brewing removes the acidity and gives it to coffee living gardeners :-) v

Michaelg is correct. Acidity isn't an issue in USED coffee grounds. Be careful with unused (FRESH) grounds they are acidic. Brewing removes the acidity and gives it to coffee loving gardeners :-) v

Oh darn it :( I thought new coffee grounds would be an easy solution for making my alkaline soil more acidic for the rugosa I plan to plant in about 10 weeks. I was going to purchase a bag of something I would not drink a.s.a.p.

Well, If I add used coffee grounds to the pot Therese Bugnet is currently in, maybe that will take it down to 7.0; the leaves will become a darker green, but just how much for a 1 gallon own root, or is this a bad idea?

Lynn

I doubt anybody has any idea about how to use coffee grounds to acidify soil or even if it does so. The pH of a substance does not tell you how that substance will affect pH, because soil chemistry is complex. To acidify garden soil, use sulfur or choose ammonium sulfate as the routine nitrogen fertilizer. If a potted plant is chlorotic, I would fertilize with Miracid.

I use the sprinkle method too. However, I don't sprinkle 'em wet. I have a spot on the porch where I place the grounds to dry. Afterward, they get dumped into a container until I accumulate enough to be worth distribution.

I'm all for adding them to the surface areas of the chlorotic as long as they are dispersed and not clump dropped. I wouldn't treat with more than 2 brews a week. My distribution is widely dispersed around the garden, with the exception of the gardenia which gets a generous helping every batch.

Now, about those slugs. The best cure is beer. Yes, beer - beer and little bowls. The best "bowls" are the old fashioned tea bag receivers - not that you young folk would have any clue about those; so, to describe them they are very small, shallow, and almost like a tiny dish with a raised edge. LOL, now that I've done all that describing I realize that a jar lid would probably work perfectly.

OK. Now for the treatment. Conditions: Rain is not forecast.
1. Take a few of these "bowls/lids" to the area where damage occurs.
2. Pull back enough soil to place them such that they are level with the soil surface. (You can do this in the morning if that's your active time).
3. But in the evening, nigh dark, go out with cheap or old beer - not what you want to drink in other words and fill them.
4. Next morning, early, take them up and dump the drowned slugs in the trash. If you're early enough, you can also catch the drunken survivors trying to escape. It's a pleasure to make an end to them as well.
Note: If you don't have a catch the first morning, give it another night. If you repeat the process about once a week for about 3 weeks to a month, you might end up slug free like me. And if you get no catch at all, then maybe the problem isn't slugs.
It is AMAZING how easy and effective this method is.

The beer does work for slugs as sandandsun mentions.

But be careful as I not only had dead slugs but a slightly drunken dog...lol

Can the deceased slugs be put in the compost pile?

Thinking Nastarana has some big slugs!

I plan on using some Sluggo, should add some iron to the soil as well.

Personally, I use 2 methods to acidify, one I put a splash of vinegar in the bird bath when I clean it (a very small splash) and then dump the water on my RdV. I also use EB Stone Rhody, Azalea and Camellia food rather than rose food on it.

On the other hand, I need to get some coffee grounds!! Lots of them, cause I am about to mulch w/ horse manure and I think I would rather smell coffee...lol

Here is a link that might be useful: Rhody, Azalea & Camellia Food 6-4-3

Yes slugs can be put into compost. There are probably slugs in there already, alive or dead.

When I come across slugs I fire them into the field behind my house. It's full of frogs.

M

This post was edited by mirendajean on Wed, Aug 7, 13 at 3:23

Killing slugs with beer is satisfying, but I read a study where they found that beer traps did not reduce damage to the garden plants. The beer traps attracted about as many extra slugs to the bed as they caught and killed.

Probably the most critical quality a gardener can possess is discernment. For success, one must be able to distinguish between fact, opinion, and fiction.

Dare I forget humor?

I have considered my 3 - 4 week recommendation for the slug beer festival and realized that in slug paradise (maybe the Pacific NW?), longer might be required.

As for attracting more slugs to the garden, they aren't winged like the japanese beetles lured to trap lures, so to that idea I discerningly say:

When slugs, like pigs, fly!

Ah ha ha ha. I had a mental picture of little flying slugs mowing through my veg like locusts. Brilliant !!!

Never underestimate how far a thirsty slug would travel for a beer.

But seriously, the effectiveness of beer traps would probably depend of what is outside the garden for whatever distance slugs can smell the beer. (Pavement or sunbaked turf vs shady weedy or mulched area.)

Mirendajean wrote:

"Acidity isn't an issue in USED coffee grounds. Be careful with unused (FRESH) grounds they are acidic. Brewing removes the acidity and gives it to coffee loving gardeners."

So how much acid is present in fresh coffee grounds? The answer to that lies not in the pH of fresh coffee (as Michaelg points out) but rather in what is called the "total acidity" of fresh coffee. Total acidity is defined in the attached link (page 202, and table 7) as the volume of 0.1 molar base required to neutralize 100 grams of fresh coffee grounds. A representative value from the linked article is 130 mL of 0.1 molar base to neutralize 100 grams of fresh coffee grounds. This amounts to .013 moles of acid per 100 grams of coffee grounds or 0.059 moles of acid per pound of coffee grounds. What effect would this have on soil pH?

A standard way to lower soil pH is to add elemental sulfur. A typical suggestion from university extension services is to add 2 pounds of sulfur per 100 square feet to lower the pH of a silt loam soil from pH 7 to pH 6. Sulfur owes its acidifying power to its oxidation in the soil to sulfuric acid. Two pounds of sulfur is 28 moles of sulfur and this should produce 56 moles of acid in the soil (because sulfuric acid has two acidic hydrogens, I'm counting each mole of sulfuric acid as two moles of acid).

So... if 56 moles of acid per 100 square feet is required to lower the pH of a typical silt loam soil by 1 pH unit, what weight of fresh coffee grounds containing 0.059 moles of acid per pound is required to get the same result? The answer is roughly 1000 pounds of fresh coffee grounds per 100 square feet.

Here is a link that might be useful: Total acidity of fresh coffee

Hey, not fair. I'm not smart enough to understand math/science with letters and words in it. :-) just kidding. It's just a bit sciency for me.

I'm an intuitive, better safe than sorry Gardner. I occasionally dump old, out of date coffee in the garden. Sometimes it's just coffee that I found I didn't like. I always toss it on my acid loving plants. Maybe it's such a small volume as doesn't matter.

I think all the little things we do add up. I do so many little things to my soil (making compost, vermicompost, adding sand, etc) I believe that everything I do works together. What I do may not apply to other gardeners. If someone only tosses 1 cup of fresh grounds a year then it doesn't matter where they toss them. If you're tossing pine mulch, unused grounds etc then it all adds up.

Hey! Does this constitute a gardening rule or a rose gardening quality? Discernment? :-)

M

If you don't want to follow Mike's math, just look at the last sentence of his post. It means, don't put 100 lb. of fresh (unused) coffee grounds on a rose unless you want to reduce the pH by 1.

I vote for discernment.

Hey! When do roses bloom on the Emerald Isle?

Well, I've used coffee grounds for years. Each rose get fours rounds of coffee grounds, each season, filter and all. I dig a hole around the drip line just deep enough to bury the ground filled filter. The roses don't seem to mind. Here's Royal William, taken today.

I have been working on a new small bed for the past 4-5 months. Thrilled to pick up five lb. bags of used grounds at coffee shops for it. About 6 bags, 2 cu. feet manure, about 50 banana peels and an inch of dried leaves. Dug down about 14 inches. An area about 40 sq. ft.

After the recent 2 inches of rain that soil still clings to the shovel like mud. I am rethinking this coffee ground business.

Jim, Your Royal William is beautiful. The color is very striking.

Just to add- last year I added a good amount of starbuck coffee grounds to my rose bush and it really shot up like 1/3 taller than usual even my neighbors noticed it and commented.