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Hydrangea fed with coffee grounds

Posted by timjc 7 (My Page) on
Thu, Mar 15, 12 at 18:16

My wife says she's read that hydrangeas do well if fed with coffee grounds. Is that the right approach?

Follow-Up Postings:

RE: Hydrangea fed with coffee grounds

well ... they dont have mouths.. so i dont know how she is going to feed them

but if you have a plain old pink only flower .. and put USED coffee grounds [she didnt mention that part.. lol] ... on one side..

you will have a half pink.. half blue flower show.. with the ones in the middle sorta both ...

did it myself last year ...

and i think i only remembered 3 basket fulls [the maker basket.. not laundry baskets] ... and i put it NEXT TO THE PLANT.. not on it .. still dont know what she means by feeding it .. yikes.. lol


RE: Hydrangea fed with coffee grounds

LOL @ Ken!

I read about that too, last summer I started dumping my used grounds on/around my plants instead of putting them in the compost pile.
By the end of the summer my compost pile was a huge fire ant bed! It was not pretty. :(

I mentioned it on a forum somewhere and was told the used coffee grounds have a neutral ph.. I'd be better off putting them in the compost pile, and pouring the left over coffee on the plants to get the acid they need to be blue instead of pink. (in our soil). So that's what I started doing.

Too soon to tell if it works or not. I'm glad to hear that it worked for Ken! I'm more hopeful now.

Unless he was joking? hmmm... I'll just have to wait and see.

RE: Hydrangea fed with coffee grounds

Here's the scoop on coffee grounds (UGC's) - the bulk of the acidity gets expressed into the coffee itself and does not remain in the grounds. They are only very slightly acidic or close to neutral in pH. While they can make a good mulch, they tend to crust over when dried so that water is repelled or does not penetrate. They are a decent, organic, low nitrogen source so semi-fertilizer in nature but are much better used as an addition to the compost, where they are considered a good "green".

Blue flowers on a hydrangea are the result of sufficient quantities of aluminum in the soil - acidic soils tend to make aluminum more available, ergo blue flowers. If you want blue flowers on your bigleaf hydrangea, try using aluminum sulfate or "hydrangea bluing" according to package directions. That combines aluminum together with sulfur, which is a natural acidifier. That will provide much more reliable results than the UCG's, which will be hit or miss at best.

RE: Hydrangea fed with coffee grounds

Ok...One of my hydrangeas is blooming: its a pale pink. :(
The coffee thing did not work for my soil.
So to today I purchased some aluminum sulfate and will be changing my fertilizer to one with more potassium and less phosphorus.

from the web site linked below:
A fertilizer low in phosphorus and high in potassium is helpful in producing a good blue color(25/5/30 is good. Potassium is the last number).

I'll give it a one year trail. If that doesn't work I'll put them in big pots to more easily control the soil ph.


Here is a link that might be useful: change the color of my hydrangeas.

RE: Hydrangea fed with coffee grounds

  • Posted by KatW none (My Page) on
    Fri, Sep 14, 12 at 2:51

I always dump my used coffee grounds on the soil below my hydrangeas...and when done regularly several months prior to blooming, the shrub is bursting with the deepest blue hydrangeas I've ever seen! The trick is to be consistent and do this as much as possible from fall through spring BEFORE they bloom. My big leaf and lace caps love coffee grounds...and since we are Seattleites, we drink a lot of good, strong, fresh coffee! :)

RE: Hydrangea fed with coffee grounds

And Seattleites have acidic soil conditions anyway.......darn hard NOT to have blue hydrangeas in this area (unless a decidedly pink cultivar - which there are -or if planted by concrete).

Once again - used coffee grounds are no more acidic than any other type of kitchen waste. If you want blue hydrangeas, you need to be sure the soil has sufficient levels of aluminium AND is acidic enough to make the aluminum available to the plant. Aluminum sulfate, aka 'hydrangea bluing', is the best method of addressing this.

RE: Hydrangea fed with coffee grounds

Indeed, as gardengal48 stated, the coffee grounds = soil acidifier hypothesis has not held up to empirical scrutiny.

I tested my own with a pH tester and they always came up between 6.8 and 7.2. The link below further dispels the myth. However, the grounds are nitrogen-rich, so there is some value there as a fertilizer or in compost.

If you want to change the color of your hydrangeas, you are better off using lime or sulfur (along with aluminum sulfate). Also, the intensity of the bloom color is not a function of acidity, but rather the plant's genetics, the weather, the soil, nutrient level, etc.

Here is a link that might be useful: Coffee Grounds Are Acidic Myth

RE: Hydrangea fed with coffee grounds

When I grew Nike in a pot, I watered with aluminum sulphate 3 times a year.1/3 cup to a gallon of water. Now I'm growing in the ground and can't seem to get the right amount on to get blue flowers. I have extremely alkaline soil-around an 8. I put sulphur on every fall, and the other in spring. We also have alkaline water.

RE: Hydrangea fed with coffee grounds

It is virtually impossible to make substanial or permanent changes to soil pH. Soils have a tendency to buffer against these changes and so will eventually return to existing pH. And sooner rather than later.

If you have alkaline soil you will always have issues attempting to get any kind of Hydrangea macrophylla blue. Combine that with alkaline water and you are facing a losing battle! Under these conditions, it would be best to grow your macrophylla in a container or raised bed/planter where you can more easily modify the soil chemistry and monitor it. And be sure to acidify your irrigation water as well - a couple of tablespoons of household vinegar in the watering can will do. Or use the aluminum sulfate.

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