On 24/11/2010 10:57, Janet wrote:
In ,
says...

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.

IME certain textures, such as sand, fine grit, wood ashes, and rough
leaves like comfrey and dried bracken, do have some protective
deterrent/ repellent effect as slugs don't like crossing them; maybe
coffee grounds work that way.

Wood ashes are pretty alkaline. Charcoal and the last bits of coke coal
seem to work for a while as slug deterrents. They don't like the rough
surface. But I think the coffee grounds effect is mainly chemical.

Regards,
Martin Brown