> One of the key functions of caffeine in the plants that produce it is allelopathy – the ability to reduce competition from surrounding species by suppressing their growth.

Wow, makes sense. I never stopped to ask why the plant produced caffeine in the first place.

Well, not only that; caffeine in plants acts as a natural pesticide.

Only if you're dumping fresh grounds directly onto the plants. Used grounds that have been composted are generally regarded as quite beneficial.

Interesting. My grandmother used to dump her coffee grounds on her roses almost every day. She swore it was what made them so big.

A lot of Starbucks stores will give you grounds for free for use in your garden. I don't know if they recommend composting first or not. My guess is they don't care.

Used grounds != fresh grounds. :)

Used, composted grounds are definitely good. Used grounds add biological material to the soil as well and lots of people have good success with that from what I understand.

whoops that's what I've been doing past few weeks...

Used grounds are probably fine if that's what you've been doing. Actual fresh grounds that have not been used to brew coffee are not a great idea.

Caffeine in a warm, moist, bacteria-rich environment, has a half-life comparable to that in the human body.

Compost your grounds, they're great.

Coffee grounds are also very acidic, so you could be killing the microorganisms in your compost.

Compost your egg shells also!

Works great for growing mushrooms though...