On 23/11/2010 23:56, Bertie Doe wrote:

wrote in message ...
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 am sure you know what I mean. You have to admire the guy who ate the
first chilli or maybe did it the second time knowing what to expect!.

Some of the things we can eat are surprising given how bad they are for
other mammals - chocolate is lethal to dogs for instance and soya beans
and some other legumes wreck most rodents reproduction cycle.

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.

I wouldn't assume that at all. 4 oz of coffee will likely contain
0.03-0.06g of caffeine. Taking 4oz as roughly ~100g = 0.05% caffeine
content. A 2% caffeine solution would be very very strong coffee the
sort that you could stand the spoon up in.

Espresso coffee can contain up to 2g/Litre caffeine which is 0.2%!

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.

I doubt it will last all summer (though it might in a greenhouse) as
caffeine is pretty water soluble and will migrate into the ground. Use
the coffee grounds directly on the soil and you might have a useful
effect. I have tried it and cannot decide if it works or not. Slug
pellets certainly do have the right effect and very quickly.

Regards,
Martin Brown