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In article ,
Martin Brown
wrote:

It is more effective just to spread the coffee
grounds around sensitive
plants like hostas and delphiniums. Turning it into a
spray isn't worth
the effort. Most things of plant origin that we
consume as stimulants
and interesting tastes were intended for chemical
warfare against plant
parasites or fungi. It is sheer good luck that they
do us no harm.

Not luck! We are evolved from a long history of
plant eaters, and
have a very high resistance to many such chemicals -
caffeine being
one. And we don't usually consume the plants which
contain ones to
which we have no resistance, however interesting they
are.


I may need your help with the maths here, as it may be
less hassle to spray the salad area on the allotment
with a gallon of fresh coffee - rather than bothering
with saving up old spent grounds.

The following are US capacity measurements:
http://preview.tinyurl.com/34gjnw2

"A 4-ounce solution of 2 percent caffeine applied to
the soil of 4-inch greenhouse pots devastated garden
slugs"

I assume they mean 4 oz of coffee contains 2% of pure
caffeine. We have to speculate as to the strength and
type of coffee and amount used.

There's no real need to use 'proper' coffee, as instant
coffee lies neatly between arabica and robusta,
according to:-
http://coffeechemistry.com/index.php...in-coffee.html

So to summarise, there are 32 cups (4 oz) in a US
gallon. I'm estimating 0.25 oz of instant per cup, so
an 8 oz jar would produce a gallon of Nescafe bliss.
Make a small adjustment for my 5 litre sprayer etc. If
it's effective and a gallon lasts all Summer, then it
could prove to be an economic method of pest control.