[CH] Re: Coffee Grounds

Wing (wing@staythorpe.freeserve.co.uk)
Wed, 23 Jun 1999 14:07:20 +0100 

Hi CH's
    Sorry it's taken a while to reply, have been away over the weekend for a
well earned rest.  I have been looking in my gardening books about the use
of coffee in the compost heap. Only two have references, both say that it
tends to stick together in the heap, (o.k so thorough turning would help
alleviate this) and that tea-leaves are much easier to compost. (maybe this
is because they are both U.K books, and that we're supposed to be a nation
of tea drinkers???) But the main reason they are not used IS because of
their acidity. The bacteria that break composts down prefer conditions that
are not too acid, hence the use of lime (calcium oxide) when building up a
compost heap. Adding coffee grounds will slow down the rate at which
the compost will break down. (on it's own it would probably be anerobic,
this would be a lot slower than an aerobic heap). Of course composting
coffee grounds in a wormery would certainly speed it up as well as adding
oxygen to the heap.

    In Camerons reply he said that his coffee grounds measured 5.5-5.6 (not
a case for much concern) however, a garden soil of 6.8-6.9 sounds a much
better level. According to various other sources (inc
Byron and Jim Cambell) this is an ideal pH for chiles, and is also where all
of the nutrients are freely available for use by plants. The physical
difference between 7.0 and 6.0 is ten times more acidity in the soil, the
difference between 7.0 and 5.0 is one hundred times more acidity, (between
7.0 and 4.0 =1,000etc). In soils of pH 5.5 and below phosphates become
locked into the soil, (this is used by plants to ripen fruit, which is what
we are trying to do) and that aluminium and manganese (which can be toxic to
plants in high doses,and human's too) become soluble. Many plants are
poisoned by only 1ppm of aluminium in the soil. I suppose what I am trying
to get at, is that, just because you can compost coffee grounds does'nt
necessarily mean that they may be good for your chiles

     Another problem experienced when composting coffee grounds or using
them as a mulch is the fact that it CAN attract fruit flies, some of whose
larvae live in the soil and just love to eat plant roots......

     Yet another problem I have seen with using coffee grounds around
plants, is mildews and botrytis building up on the surface of it, these
thrive in cool, humid and damp conditions (most of U.K then...) and CAN
result in
yellowing of lower leaves and loss of vigour in the growth of plants, Downy
mildew actually penetrates inside the stems and may eventually kill plants..
I am a great believer in "cleanliness is next to chileness" and that trying
to avoid attracting pests and diseases near to what I love best is better
than trying to cure them afterwards..

    Now, I am not saying we cannot use coffee grounds in horticulture, and
am sure they have their uses, either for composting and then adding to
plants that prefer a more acid soil than chiles do, (ie. heathers azaeleas,
rhodo's and blueberries etc) or for lowering the pH of a high alkaline soil.
After all, in various European countries when brick buildings are being
knocked down instead of removing the rubble they are grinding it up on the
spot and planting into that... neat eh! (although I wouldn't suggest using
this for chiles either, too much lime this time) this is the same as Lukes
situation in Oz and coffee can be used if composted and the right plants are
chosen to grow in it. I also drink lots of freshly ground coffee, and it
does seem a waste not to use it but, I PERSONLY prefer not to, after all
even the most hardened coffee drinker could'nt produce more than a couple of
80 litre bags full of coffee grounds to compost in a season... could they
(oh #!@# hope this has'nt opened up another "can of coffee grounds" or worms
etc please don't email me on this one aagghh!)

    Anyway sorry this was a long one and if coffee works
    for you great use it...there are no hard and fast rules in horticulture.

may all your flowers be pollinated.....

..........wing..........

P.S Cameron it's Mr wing