"David" wrote in message ...

Having been reminded that coffee grounds are a folk remedy for deterring
slugs, I looked it up online.

Apparently it is illegal to use any untested product as a chemical
deterrent.

Mulching to add organic content is fine, though.......

Ignoring the above for the moment, has anyone tried this and does it work?

Yes it works. 3 years ago I put some slugs and snails on a piece of slate
and added coffee mixed with grounds. The slugs started to dissolve :-

https://www.dropbox.com/s/72kze5xc3x..._2206.JPG?dl=0

I popped a large pot over and investigated the following morning. No remains
of the slugs but the 3 snails had climbed to safety, up the inside of the
flower pot :-

https://www.dropbox.com/s/lmub2irr51..._2215.JPG?dl=0

I'm not sure how much damage coffee does to the soil biology, I would
therefore proceed with caution when using it as a general mulch. You need to
get some sealed containers with some garden bugs and experiment with coffee
grounds at varying doses.

Getting hold of sufficient quantities of coffee grounds is straightforward
as most cafes will donate, if you ring them beforehand. In fact, Howard
Shultz former CEO of Starbucks started a "Grounds for your Garden" project.
Wet "pucks" of coffee grounds are quite heavy, so double-bag for safety.

The slugs' natural enemy are nematodes but it's probably beyond the scope of
an amateur to test caffeine v nematodes. I haven't tested grounds on garden
worms but the para "Ecological Effects" suggests it's Ok :-

https://en.wikipedia.org/wiki/Coffee#Biology

Your biggest hurdle will be protecting your barricade of coffee grounds from
heavy rain. Constant topping-up, could turn your hosta patch into a sterile
desert. One of the Hawaii universities started a study (about 10 years ago)
on the bio effects of coffee in the soil. Maybe they ran out of money but so
far nothing has been published. Anyhoo experiment, proceed with caution and
.... good luck.