Coffee Grounds in the Garden: Benefits, Myths & Cautions

Are coffee grounds good for plants? Yes, but with caveats.

Pros

• Excellent organic matter (carbon + nitrogen).
• Near-neutral pH (~6.7) after brewing—safe for most plants.
• Earthworms love them → improved soil structure.
• Slug barrier: slugs avoid coffee grounds.

Unresolved Science

Coffee contains volatile compounds (e.g., 2-furylmethiol) that may inhibit other plants—coffee plants themselves are allelopathic. No definitive studies on used grounds' allelopathy. University research pending.

Practical Advice

• Use grounds as mulch/compost additive.
• Monitor plants for negative effects (yellowing, stunting).
• If issues arise, stop use.
• Otherwise, enjoy the earthworm boost and slug deterrence.

Science hasn't settled it, but anecdotal success is widespread. Use wisely, observe closely.